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INTRODUCTION
Temporal Discounting Overview
People consistently prefer immediate rewards to delayed rewards even when the
immediate reward is of lesser value. Individual preference for smaller, immediate
rewards over larger, delayed rewards is called either temporal discounting or delay
discounting. Such discounting represents the decrease in the subjective value of rewards
over time (i.e., after a delay). Measuring temporal discounting usually takes the form of
asking individuals to choose between a smaller reward available immediately and a larger
reward available after a delay. With increasing delay, progressively smaller rewards are
preferred. This decline can be described by a hyperbolic function [Y = A / (1+ k D)] in
which k is the slope constant. Individual differences in slope constants (discounting
rates) appear to be stable. Simpson and Vuchinich (1998), for example, found that the
values obtained before and after a week interval are highly correlated (r = .906).
Assuming such stability, patterns of temporal discounting have often then been viewed as
individual differences similar to personality traits.
Discounting rates correlate with measures of trait impulsiveness (Ostaszewski,
1996) and are considered by some authors to define impulsiveness (e.g., Rachlin &
Raeneri, 1992). Researchers have also found that individuals with addictions to nicotine,
alcohol and heroin discount more steeply than individuals without those addictions (see
Kollins, 2003, for a review). Given the relationship between temporal discounting,
impulsiveness and addiction, some authors have suggested that temporal discounting
research may be useful in designing drug interventions (Bickel & Marsch, 2001).
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The exact mechanism for the relationship between steeper temporal discounting
rates and impulsiveness is unclear, however. We shall consider two cognitive hypotheses
for explaining at least some of the variance in discounting rates here: a working memory
hypothesis and an ego-depletion hypothesis.
Working Memory and Temporal Discounting
Hinson, Jameson, and Whitney (2003) speculated that some individuals might
discount steeply due to a dysfunction in the working memory system. They defined
working memory as “that part of the cognitive system that is used to hold a limited
amount of information in the focus of attention” (p. 299). The working memory system
is thought to consist of a central executive that, in turn, consists of two slave systems
which actively maintain representations: a visuo-spatial sketchpad (for maintaining
images) and a phonological loop (for maintaining auditory information) (Baddeley,
1999). Hinson et al. (2003) described the working memory system as also including “an
executive control subsystem that manages the selection of information for further
processing, the inhibition of no-longer relevant information, and the coordination of
feedback with continued information processing” (p. 299). Although there is some
debate as to the definition and operation of working memory, most researchers consider
the executive control system, or the central executive, as critical to the definition of
working memory (Oberauer, Schulze, Wilhelm, & Sub, 2005). Kyllonen (1990), in fact,
argued that the central executive aspect of working memory was central to all cognitive
processes. Thus, “executive control refers to those abilities involved in allocating
attention to both internally maintained and externally presented information during the
performance of complex tasks” (Whitney, Jameson, & Henson, 2004, p. 417).
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Hinson et al. (2003) then suggested two mechanisms by which working memory
deficits might lead to steeper temporal discounting. First, individuals with less working
memory capacity may be less able to prevent extraneous information from interfering
with their decision-making processes. Thus, these individuals would make quick,
impulsive decisions before extraneous information interrupts their decision making.
Second, limited working memory capacity may leave individuals unable to properly
process the relative value of the available rewards. They discount steeply because they
lack the cognitive resources to evaluate delayed rewards correctly. They may not
distinguish well between the value of immediate and delayed reward unless the disparity
between the two is strikingly large.
This theorizing has led to research examining temporal discounting as reflecting a
stable (though dysfunctional) pattern of cognitive processing that results in impulsive
decision-making in a variety of domains. It has been found that requiring participants to
complete a task that occupies working memory while completing the temporal
discounting task decreases the value of delayed rewards. Ebert (2001) told half of his
participants to monitor an auditory tone track for a specific pattern of tones while
completing a discounting task. Participants evaluated potential rewards (e.g., a
television, a weekend ski trip) on a continuous four-point scale ranging from not at all
valuable to extremely valuable to me. The hypothetical rewards were delayed for a day, a
month, or a year. Participants who performed the monitoring task discounted the value of
the delayed reward more steeply (i.e., rated delayed rewards as less valuable) than
individuals who did not perform the monitoring task.
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A similar effect on temporal discounting has also been demonstrated using a more
standard discounting procedure with multiple delays. Hinson et al. (2003) instructed
participants to remember a string of numbers during the discounting task and later recall
the position of one of the numbers (e.g., “What number was to the right of 3?”). Control
participants were not told to remember the digit string. Participants who maintained the
digit string in memory during the discounting task discounted more steeply, as predicted.
To extend the findings of the first experiment, Hinson et al. (2003) next increased
the demands of the task itself in a second experiment, varying the number of decisions
participants made at each delay. Rather than offering an immediate reward versus a
single delayed reward, the participants were required to choose either an immediately
available reward versus either of two different delayed rewards or either of three different
delayed rewards (different amounts of money at different delays). Increasing the number
of options led to steeper discounting, demonstrating that increasing the cognitive
complexity of the task itself does lead to steeper temporal discounting. Additionally,
Hinson et al. (2003) compared discounting rate to self-reported impulsiveness with the
Barratt Impulsivity Scale (BIS-11) (Barratt & Stanford, 1995) and to executive
dysfunction with the Dysexecutive Questionnaire (DEX). The DEX (Burgess, Alderman,
Evans, Emslie, & Evans, 1996), which asks participants to rate the prevalence of
executive function deficits (e.g., working memory difficulties) in their daily lives, is
highly correlated with the BIS-11 (r = .76, p < .01), indicating that impulsivity is
associated with executive dysfunction. As expected, individuals who scored higher on
either the BIS-11 or the DEX (or both) discounted more steeply than individuals with
lower scores. Again, increasing the demands on working memory either through
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performing a working memory task such as remembering a digit-string during the
discounting task or through making additional decisions within the discounting task
produced higher discounting rates.
These studies indicate that working memory is involved in temporal discounting
but do not answer Hinson et al.’s (2003) question as to whether steeper temporal
discounting results from misjudging the value of the delayed rewards or from insufficient
resources to inhibit extraneous information from interfering with their decision. Hinson
et al.’s choice of manipulations also raises some additional questions. The manipulation
in the first experiment (simultaneously remembering a span of digits) is a traditional
manipulation of working memory. The second manipulation (increasing the number of
choices available), however, also increased the demands of the task itself and so the
relationship between increasing the number of decisions in the discounting task and
working memory is less clear. Deciding between a number of options may impact the
immediate decision or there may be a cumulative impact of making a series of decisions
that would be greater for those who chose from among more options. Certainly the effect
of these manipulations on temporal discounting rates seems to reflect an effect of the
resource limitations of working memory. The fact that including a second task,
increasing the number of options in the discounting task, and scoring higher on a measure
of executive dysfunction all have similar effects on discounting rates implies that they all
represent the effect of working memory deficits on discounting rates.
The ability of a working memory task to impair a concurrent working memory
task is well documented. But, a question that then emerges is whether the demands of a
prior completed cognitive task could lead an individual to be more impulsive in a
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subsequent decision-making task. Could an individual’s working memory capacity be
exhausted through a primary executive function task such that performance on a
subsequent task would be affected? This is the approach taken by ego-depletion theory.
Ego-depletion Theory
There appears to be little research examining the impact on a second task if
working memory capacity or executive control has been depleted on a previous task.
The evidence, however, does indicate that if inhibition of some activity is required in one
task, there is less ability to inhibit behavior in a subsequent task. For example,
individuals who engage in a thought suppression task are less able to resist an impulsive
behavior that they believe has negative consequences. Specifically, social-drinkers who
engaged in a thought-suppression task subsequently drank more alcohol than participants
who did not engage in the task (Muraven, Collins, & Nienhaus, 2002). The thought-
suppression group was instructed to resist thinking of a white bear (see Wenzlaff &
Wegner, 2000, for a review of this methodology) and a control group was instructed to
complete arithmetic problems, then both groups were given the opportunity to sample
beer. The participants were warned to limit their alcohol intake because after the beer
sampling they would compete in a driving simulation and could win a prize if they
performed well. Participants who engaged in the thought-suppression task consumed
more alcohol and had a higher blood alcohol content than individuals who completed the
arithmetic problems.
Many behaviors that seemingly require conscious effort, however, might actually
result from automatic processes guided by environmental cues (Bargh, 1996). It appears
that people have a limited capacity to resist the automatic behaviors that are elicited by
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these cues. Freud’s term “ego” has been used to conceptualize this limited capacity to
resist impulsive, automatic behavior in the short term. Resisting one impulsive behavior
reduces the capacity to inhibit subsequent impulsive behavior. The reduction of this
capacity is called “ego-depletion.” Research such as Muraven et al.’s (2002) study of
drinking supports the notion that ego-depletion can lead individuals to engage in risky
behavior that they might otherwise resist.
Baumeister, Bratslavsky, Muraven, and Tice (1999) demonstrated in a series of
experiments that performing an “ego-depletion task” decreased subsequent self-
regulation in a variety of contexts. Self-regulation refers to the individual ability to resist
temptation and persist in unpleasant behavior. The paradigm for these experiments was
to induce ego-depletion and then examine the participant’s ability to persist in (i.e., resist
quitting) a subsequent, relatively unpleasant task. In their first experiment, each of the
participants, tested individually, was presented with both a plate of chocolates and a plate
of radishes. Some participants were told to eat only chocolates and some were told to eat
only radishes. Participants in each of these conditions were asked to sample at least three
of their assigned food and the experimenters covertly observed the participants through a
one-way mirror in an adjoining room to ensure the participants followed their instructions
(the number of radishes or chocolates consumed by each participant was not reported).
The third group of participants was not presented with any food. The participants were
then instructed to complete an impossible figure-tracing task, which involved tracing a
geometric figure without lifting the pencil from the paper or retracing the drawn line.
The authors argued that self-regulation was required to persist in the task given the
frustration that would accompany repeated failure. The amount of time the participants
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spent attempting to complete the impossible task was the dependent variable. The control
group of participants, not presented with any food, was only instructed to complete the
figure-tracing task. The experimenters hypothesized that resisting eating the chocolates
and persisting in eating radishes would result in ego-depletion and less persistence in the
figure-tracing task. As predicted, the participants who only ate radishes did not persist in
a subsequent figure-tracing task as long as those who ate chocolates or as long as those in
the control group. Participants’ times in the latter two groups did not significantly differ
from each other. In another experiment, individuals who suppressed displays of emotion
during a funny movie or during a sad movie subsequently solved fewer anagram puzzles
than participants who did not suppress their emotions.
The experimenters also demonstrated that simply making a decision could also be
ego-depleting. The literature regarding cognitive dissonance, the authors noted,
demonstrates that attitude change only occurs when the individual freely chooses to
engage in counter-attitudinal behavior. In this experiment, participants were told to read
a written speech in a persuasive manner. Utilizing a traditional cognitive dissonance
paradigm, some participants were told to read a counter-attitudinal speech (i.e., a
persuasive speech with which they did not agree), some participants were told to make a
pro-attitudinal speech (i.e., a persuasive speech with which they agreed), and some
participants were given a choice to read either speech. Those in the choice group were
informed that choosing to deliver the counter-attitudinal speech would be more beneficial
to the researcher but that the final decision belonged to the participants. As the
researchers predicted, participants who chose which speech to read did not persist as long
in a subsequent task as participants who were not given a choice, regardless of whether
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the participant agreed with the content of the speech. The authors concluded that the act
of making a decision itself is also ego-depleting. Thus, it is concluded that the “ego” is a
limited resource that is utilized in deliberate acts such as making decisions and regulating
behavior. The ego can be depleted by many activities and this depletion leads to
impaired performance on a subsequent task.
Comparison of Ego-Depletion and Working Memory Models
Differences. There is one crucial distinction between the working memory
literature and the self-regulation literature. Specifically, participants in Hinson et al.’s
(2003) study engaged in the working memory task (either remembering a digit-string or
making a series of decisions) as part of the temporal discounting task and simultaneously
completed the temporal discounting task. An important aspect of the ego-depletion
literature, however, is that the first task in which the participant engages is completed
before the second task begins. Hence, the “ego” is not actively occupied; it is
temporarily depleted from a previous activity. The central distinction between the two
literatures, therefore, is that working memory models describes the simultaneous
expenditure of resources on two tasks, while ego-depletion describes a decline in
resources that transfers from one task to the next.
Similarities. Ego-depletion theory appears to be similar to models of working
memory and executive function in other ways, however. Conceptually, ego strength and
working memory both involve a limited cognitive capacity. Generally speaking, the ego-
depletion literature complements the research of Ebert (2001) and Hinson et al. (2003) on
temporal discounting and working memory. The methodology is similar; participants
who performed a task involving either working-memory or self-regulation performed
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more poorly (or impulsively) on another task performed either concurrently (in the case
of working memory) or subsequently (in the case of ego-depletion) than those who did
not do the distracting or depleting task. Both lines of research assume a limited resource
that can be temporarily reduced, concluding that the ability to regulate their impulsivity
can also be temporarily reduced.
There are also more specific similarities between the literatures. First, making a
series of decisions affects both ego-depletion and working memory. Baumeister, Tice,
and Twenge (1999) found that making a series of decisions constitutes an ego-depleting
task. The researchers instructed participants to provide a number of ratings on a
commercial product’s features. The participants were then given the opportunity to earn
money by imbibing an aversive drink (unsweetened Kool-Aid); participants were paid for
every cup they drank. Participants who previously made decisions consumed
significantly less of the drink than a control group who did not make the series of
decisions. This parallels Hinson et al.’s (2003) finding that increasing the number of
options in a temporal discounting task led participants to be more impulsive in their
decision-making. Taken together, these results indicate that making a series of decisions
leads to both ego-depletion and steeper temporal discounting.
Second, manipulating task complexity affects both ego-depletion and working
memory. For example, Baumeister et al. (1999) told participants to read a manuscript
and draw a line through every “e” that appeared. Half of the participants were instructed
not to draw a line through any “e” that appeared next to a vowel or one letter away from a
vowel (such that a participant would not draw a line through the word “vowel”).
Participants receiving this extra instruction performed less well on a subsequent task
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compared to the group who merely drew a line through every “e.” Fulfilling this extra
instruction would require working memory in a manner similar to the additional digit-
task of Hinson et al.’s (2003) experiment. Participants in that experiment remembered a
series of digits; participants in Baumeister et al.’s (1999) experiment remembered their
specific instructions.
Findings such as these led researchers to examine the impact of ego-depletion on
working memory tasks. Schmeichel, Vohs, and Baumeister (2003) told participants to
watch a video recording of a woman being interviewed. As the woman spoke, words
were displayed across the bottom of the screen; half of the participants were told to
ignore these words and the other participants were given instructions regarding the
words. Participants then completed the analytical portion of the Graduate Record Exam
(GRE). They found that participants told to ignore the displayed words subsequently
performed worse on the GRE analytic test. Noting that Baddeley (1996) argued that
complex reading comprehension involved the central executive component of working
memory, the researchers replicated the experiment with the reading portion of the GRE.
Similar results were obtained; participants in the ego-depletion group did not perform as
well as the participants in the control group. Thus, this study provides some evidence
that performing an ego-depletion task impairs subsequent performance on cognitive
tasks.
Present Study
To date, no researchers have studied the effect of ego-depletion on temporal
discounting. The purpose of the present experiment was to take this next logical step.
Based on the research discussed thus far, there is sufficient reason to believe that the two
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concepts are related. Though the ego-depletion literature is small, it is conceptually
similar to research on working memory and temporal discounting in several ways. First,
Baumeister, Tice, and Twenge (1999) found that participants asked to make more ratings
on features of a car subsequently did not continue as long in a subsequent task as
individuals making fewer ratings; likewise, Hinson et al. (2003) found that individuals
who were given more options in the discounting task also discounted more steeply.
Second, in Baumeister et al.’s (1999) experiment, participants who were instructed to
draw a line through every “e” unless the “e” was next to or one letter away from a vowel
did not persist as long in a subsequent task as individuals who were told to draw a line
through every “e.” Similarly, individuals instructed to remember a span of digits
discounted more steeply than individuals who were not instructed to remember the digit
span. Finally, Schmeichel et al. (2003) demonstrated that an ego-depletion task led to
impairment on a subsequent reasoning task that involves the central executive.
Demonstrating an association between these concepts would add a new dimension
to the discounting literature. Much of the research in temporal discounting has
concentrated on identifying individual differences that predict differential discounting
rates. Hinson et al.’s (2003) research reflects the only study attempting to alter
discounting rates of participants with a cognitive (i.e., working memory) manipulation
and the researchers found that a simultaneously performed working memory task
increases discounting rates of participants. The present experiment tests the hypothesis
that an ego-depletion task would also lead to steeper temporal discounting. Such a
finding would indicate that discounting rates could result from a task completed
previously as well as from a second task completed simultaneously.
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We, therefore, utilized one of the manipulations used by Baumeister et al. (1999)
to produce ego-depletion and examined the effect of this manipulation on temporal
discounting rates. Baumeister et al. (1999) used four tasks: delivering a counter-
attitudinal speech, resisting eating chocolates, crossing out the letter “e” in a manuscript,
and suppressing emotion during a movie. Of these tasks, one of the most powerful
manipulations and yet the simplest to replicate is the “e” manuscript editing task.
Participants were told either to draw a line through only every “e” (low ego-depletion) or
to draw a line through every “e” which is not adjacent to a vowel or one letter away from
a vowel (high ego-depletion). This task reliably produces ego-depletion in participants
(Baumeister, 2005, personal correspondence). Therefore, it was predicted that
individuals given the more complex task would subsequently demonstrate steeper
temporal discounting.
As soon as the ego-depletion task was completed, participants were instructed to
rate how impulsive and controlled they felt at that moment. It was hypothesized that
individuals who completed the more difficult editing task should report feeling more
impulsive and less self-controlled than individuals who completed the less difficult task.
There was still some risk, however, that the manipulation would affect working memory.
Therefore, to separate the effects of ego-depletion from working memory, at the end of
the experiment the participants were moved to a separate room and given an incidental
memory test for various characteristics of the items in the testing room, such as the
number of pens on the desk and the color of the chair. Lavie (2001) demonstrated that
when individuals’ working memory is occupied with a task, their ability to ignore (i.e.,
inhibit the perception of) extraneous information is impaired. If working memory, rather
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than ego-depletion, was affected by the manipulation, then the individuals with the more
difficult editing task should have had more difficulty ignoring extraneous details in the
room and thus demonstrate better recall on the memory test. Indeed, Hinson et al. (2003)
suggested that individuals who are unable to prevent extraneous information from
interfering with a working memory task might adopt an impulsive decision-making style.
If this alternative hypothesis was true, then the individuals who performed better on the
memory task should also discount at higher rates. It was hypothesized, however, that
there would be no difference in memory test scores across conditions as working memory
would not be affected by the manipulation and that scores on the memory test would not
be related to temporal discounting rates.
Separate from the effect of ego-depletion, the present study also explored the
specific relationship between discounting rates and trait impulsivity. Hinson et al. (2003)
demonstrated that the Barratt Impulsivity Scale (BIS-11) predicted temporal discounting
rates. The present study attempted to replicate this result. In addition, the Self-Control
Scale designed by Tangney, Baumeister, and Boone (2004) was also administered. It was
hypothesized that participants discounting more steeply should report less self-control, as
well as more impulsivity, than the participants who discounted less steeply.
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METHOD
Participants
The participants in this study were 87 undergraduate students (44 females and 43
males) who received partial credit for their psychology course by participating in the
experiment. Their ages ranged from 18 to 23 years. The participants volunteered for the
experiment through a university-wide Experimetrix program. The program described the
study as an essay editing and decision-making task.
Design
This experiment used a between-subjects design with two levels of ego-depletion
(low and high) and gender as independent variables and discounting slope (K-values) as
the dependent variable. It was predicted that participants in the high ego-depletion
condition would discount more steeply (have larger K-values) than participants in the low
ego-depletion condition regardless of gender. Additionally, a multiple regression was
performed with ego-depletion condition, gender, BIS-11 score and Self-Control Scale
score as predictor variables and K-values as the dependent variable. It was predicted that
high ego-depletion, higher BIS-11 scores and lower Self-Control Scale scores would be
associated with steeper temporal discounting.
Materials
Self-Control Scale (Tangney, Baumeister, & Boone, 2004, Appendix A). This is a
thirty-six item scale that measures self-control. Participants evaluated how well each of a
series of statements describes them. Thus, participants assigned statements such as “I am
good at resisting temptation” a rating from a scale of 1 (not at all) to 5 (very much).
Higher scores on the scale reflected more self-control. The Self-Control Scale has
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demonstrated strong internal consistency (alpha = .89) and test-retest reliability (r2 = .89,
for participants tested twice with a three week interval between sessions) (Tangney, et al.,
2004).
Barratt Impulsivity Scale (BIS-11) (Barratt & Stanford, 1995, Appendix B). The
BIS-11 consists of thirty statements such as “I get bored easily when solving thought
problems” and “I do things without thinking.” Participants rated how relevant the
statements are to themselves on a scale from one (rarely/never) to four (almost
always/always). Higher scores on the BIS-11 reflect higher levels of impulsivity.
The BIS-11 scale has six first-order factors: attentional impulsivity, motor
impulsivity, cognitive instability, cognitive complexity, perseverance, and self-control
(Appendix C).
Momentary Impulsivity Scale (Appendix D). This was a five-item scale designed
specifically for this study. Participants rated on a scale from one (not at all) to five (very
much so), and in the following order, how well the terms “creative,” “self-controlled,”
“sympathetic,” “impulsive,” and “organized” described how they felt following the ego-
depletion task. Only the two items “self-controlled” and “impulsive” were scored, the
others being distracters.
Incidental Memory Task (Appendix E). The incidental memory task consists of
twelve fill-in-the-blank questions that test participants’ ability to recall specific details of
the testing room and the testing apparatus. The questions asked about topics such as the
color of the chair in which the participant sat, the number of pens on the table, and
whether or not the room had a fire alarm.
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Procedure
Before the experiment, participants were assigned to either the high ego-depletion
or the low ego-depletion condition. In order to balance gender across the conditions, all
participants within each gender were paired in order of their assigned times (e.g., the first
and second male were paired, the third and fourth male were paired, etc.). A coin-toss
assigned the first member of each pair to one condition and the other member of that pair
was assigned to the opposite condition. For example, a coin-toss determined that the first
male would be in the low ego-depletion condition and then the second male to arrive was
assigned to the high ego-depletion condition. In this manner, gender was balanced for
both the high ego-depletion (22 males, 22 females) and the low ego-depletion (21 males,
22 females) conditions.
Participants completed the experiment individually in thirty-minute sessions.
When they arrived at the lab, each participant was ushered into an isolated 7’ by 7’ room
and seated in front of a computer monitor. They were then instructed to sign an informed
consent form that stated that they would be completing an editing task, a decision-making
task, and measures of cognition and personality. The experimenter explained that during
the course of the experiment, he would be seated in another room and would
communicate through an intercom on the desk next to the computer monitor. Three
folders were also on the desk. The first contained the essay to be edited, the second
contained the momentary impulsivity scale, and the third contained the Self-Control
Scale and the BIS-11.
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Participants then received instructions regarding the temporal discounting task
and completed some demonstration items. The experimenter read the instructions aloud
to the participant as he or she also read them from the computer screen:
“In this task we are interested in what value people put on money they can get in
the future compared to money they can get right now. Suppose you could get
$1000 in the future but could get some lesser amount right now. For example,
suppose you could get $1000 if you were willing to wait a month, but could get
$750 right now, without waiting. Which would you choose: $1000 in a month or
$750 right now? Suppose you could get $1000 in six months or $500 now.
Which would you choose? Here are some more examples:”
The experimenter then left the room and the participant was presented with the
following choices: $1000 in two weeks or $850 now, $1000 in two weeks or $900 now,
$1000 in two years or $5 now, and $1000 in two years or $10 now. Participants were
instructed to answer by stating the numerical value of the amount they would prefer (e.g.,
saying “one thousand” or “nine hundred”). Once these choices were completed, the
experimenter entered the room and provided these instructions:
“The actual task you do will involve $1000 and the delays will range from one
week to five years. At each delay, you will be given a series of choices between
the $1000 available in the future and some other amount right now. For each
choice, say which you would prefer, the $1000 to be received at some future time
(a month, a year, etc.) or the alternative amount right now.
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Just say, ‘$1000’ (which will be in the left box on the screen, along with the delay
period) or say the amount in the box on the right. When you make your choice,
the experimenter will advance to the next set of choices.”
After any participant questions had been answered, the experimenter instructed
the participant to open the first folder and edit the essay inside (Appendix F). Half of the
participants were instructed to draw a line through each “e” appearing in the text; half of
the participants also were instructed not to draw a line through any “e” which appeared
next to a vowel. Participants were told that they had seven minutes to complete the task
to the best of their ability. Baumeister et al. (1998) did not provide temporal parameters
to the editing task in the original study; participants worked until they completed the
editing task (though each participant completed the experiment in 30 minutes). In this
study, however, the duration of time spent completing the task was controlled. In
Baumeister et al.’s (1998) first study, the amount of time spent eating either radishes or
chocolates was five minutes. It was presumed, therefore, that seven minutes of text
editing should lead to differential ego-depletion effects between groups. The
experimenter then left the room and communicated via the intercom for the rest of the
experiment. Once the seven minutes had elapsed, the participants were told to return the
essay to the first folder. The experimenter then instructed the participant to complete the
momentary impulsivity scale in the second folder and return the completed scale to the
second folder.
Participants then completed the temporal discounting task (the “economic
decision-making task”) (see Appendix G). The task consists of two complementary
procedures: ascending titration and descending titration. In ascending titration, the
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immediately available amount starts at $1.00 and is increased until a point of indifference
between the delayed and immediate values is found. For example, a participant would be
asked if he or she would prefer to receive $1 now or receive $1000 in one year. If the
participant chose the delayed amount, then the experimenter would ask the participant to
choose between $5 now and $1000 in one year. Holding the delay constant, the
immediate amount would be increased until the immediate amount is preferred. The
preference switch is recorded as the relative value of the delayed reward. In descending
titration, the experimenter starts at $1000 and the amount available immediately is
decreased. For example, a participant would be asked if he or she would prefer $1000
now or $1000 in a year. The immediate value is then decreased until the participant
prefers the delayed amount – the preference shift is in the opposite direction for the
descending rounds – and this value is recorded as the relative value of the delayed
reward. By averaging the scores for a participant in ascending and descending rounds at
a single delay, a more accurate estimate of the relative value of delayed rewards is
obtained than with either procedure individually. Delays were one week, one month,
three months, six months, one year, three years and five years (see Appendix H). The
titration procedure is commonly used and reliably (r = .906) measures individual
temporal discounting (Simpson & Vuchinich, 1998).
Once that task was completed, participants completed the BIS and the Self-
Control Questionnaire. As soon as the participants completed these scales, they were told
to replace the scales in the folder, exit the testing room and complete the memory test in
another room. Once this test was completed, the participants were instructed to leave
21
their email address to receive a full explanation of the study. Participants were then
thanked for their participation.
22
RESULTS
Preliminary Data Reduction
The average of the discounted values at each of the seven delays for each
participant were fitted to the hyperbolic function V = A / (1 + k D), in which V represents
the discounted value of the reward, A is the absolute value of the reward ($1000), D
represents the delay in weeks, and k is the slope constant. The larger the value of k, the
steeper the delay function. The raw data, K-values and R2, the least squares measure of
curve fit, are summarized for each subject in Appendix I. The mean K-value was .033,
SEM = .009, and the mean R2 was .802, SEM = .025. Because the K-values were strongly
positively skewed, the largest five outlying scores identified by SPSS 13 were dropped
from subsequent analyses. Additionally, the remaining scores were transformed to
logarithms using the formula log K= log 10 (K + 1) to reduce the score range. The value 1
was added to K to ensure that negative or zero values would be included. Of the included
scores, the mean log K-value was .006, SEM = .0001, and the mean R2 = .797, SEM
= .026. These transformed values were used in all subsequent analyses and will be
referred to simply as K-values.
Manipulation Checks
There were four measures of the manipulation’s effectiveness. First, the number
of lines of text that the participants completely edited was counted. Participants in the
high ego-depletion condition were expected to complete fewer lines than the participants
in the low ego-depletion task, one measure of whether the participants were following
instructions. As expected, the low ego-depletion group edited more lines of the
manuscript (M = 24.63, SEM = .671) than high ego-depletion participants (M = 17.64,
23
SEM = .655), F(1, 80) = 55.45, p < .001.
Second, participants rated their feelings of self-control immediately following the
ego-depletion task. Contrary to the hypothesis, the high ego-depletion group did not
show a lower level of self-control (M = 5.81, SEM = .212) than the low ego-depletion
(M = 5.80, SEM = .217), F(1, 80) = .001, p = .975.
Third, participants rated their feelings of impulsivity immediately following the
ego-depletion task. It was hypothesized that participants completing the difficult ego-
depletion task would report more momentary impulsivity than participants completing the
less difficult task. Contrary to the hypothesis, there was no significant difference
between the impulsivity scores of participants in the high (M = 4.83, SEM = .228) and
low (M = 4.63, SEM = .234) ego-depletion conditions F(1, 80) = .406, p = .526.
Lastly, the fourth measure of the effectiveness of the manipulation was the
incidental memory task for objects in the experiment room. It was hypothesized that the
manipulation would induce ego-depletion but working memory engagement would not
differ significantly between the groups. As expected, there was no difference between
the memory task scores of the high ego-depletion (M = 4.21, SEM = .26) and low ego-
depletion (M = 4.48, SEM = .26) groups, F(1, 80) = .504, p = .48. However, this is only
meaningful in the context of ego-depletion demonstrating an effect on the immediate
measure of self-control and impulsivity. By itself, this is not evidence for a successful
manipulation of ego-depletion as it does not demonstrate an effect of ego-depletion.
Analysis of Discounting
Effect of ego-depletion and gender on discounting rates Ego-depletion
condition and gender were the independent variables in a 2 x 2 between-subjects
24
ANOVA with K-values as the dependent variable. The results are summarized in Tables
1a and 1b. Only the main effect of gender was significant (p = .001). Males discounted
more steeply (M = .010) than females (M = .003).
Table 1a
Descriptive Statistics for the Effect of Gender and Condition on K-values
Group Mean Std. Error N
Males
Low ego-depletion .007 .002 19
High ego-depletion .013 .002 22
Female
Low ego-depletion .004 .002 21
High ego-depletion .002 .002 22
Table 1b
Univariate ANOVA Examining the Effect of Gender and Condition on K-values
Source Sum of Squares Df Mean Squares F Sig. Eta2
Gender .001 1 .002 11.004 .001 .124
Ego-Depletion Condition .0001 1 .0001 1.072 .304 .014
Gender * Ego-Depletion Condition .0002 1 .0002 2.615 .110 .032
Error .008 78 .0001
Total .010 81
Regressions of condition, gender, BIS-11 and Self-Control Scales on K-values
A simultaneous multiple regression was conducted to compare the amount of
variance in K-values accounted for by ego-depletion condition, gender, BIS-11 scores,
and Self-Control Scale scores. The variables accounted for a significant portion of the
25
variance, F(4, 77) = 3.614, p = .009. As Table 2 indicates, however, only gender
explained a significant portion of the variance in K-values.
Table 2
Results of simultaneous regression of gender, BIS-11 scores, and Self-Control Scale
scores on K-values
Variable Unstd. B SEM Beta (std) T Sig. Semi-Partial Correlations
Constant .042 .020 2.126 .037
Gender -.008 .002 -.358 -3.410 .001 -.357
Ego-Depletion Condition
.003 .002 .128 1.205 .232 .126
Self-Control Scale Score
-.0001 .00009 -.189 -1.560 .123 -.163
BIS-11 Scores -.0002 .0001 -.129 -1.050 .297 -.110
Note. Dependent Variable = K-values.
In summary, the principle finding of this study is that males (M = .010)
discounted steeply more than females (M = .003).
26
DISCUSSION
Ego-depletion and Temporal Discounting
The results did not support the hypothesis that ego-depletion would lead to steeper
discounting rates. The participants in the high ego-depletion condition completed more
of the editing task when instructions were easier, as they should have, indicating that the
participants did follow instructions. However, the high ego-depletion condition did not
affect immediate measures of either impulsivity or self-control. This could indicate
either that the manipulation failed or that the measures were inadequate. There is no
evidence that working memory demands differed significantly between the groups given
that there were no differences in the memory test at the conclusion of the experiment.
Given the failure to affect immediate ratings of impulsivity or self-control and the lack of
differences in the memory test scores, the group difference in K-values that emerged in
the present study was due to gender and not related to either inadvertent manipulation of
working memory or manipulation of ego-depletion. The question of whether successfully
manipulating ego-depletion affects K-values remains unanswered.
As no significant differences were found between the high ego-depletion and low
ego-depletion groups, it is important to explore possible reasons that the manipulation
failed. First, in Baumeister et al.’s (1999) original task, participants completed the entire
manuscript before beginning the subsequent task. In this study, participants were given
seven minutes to complete as much of the manuscript as possible. Perhaps task
completion is an important element in ego-depletion. This argument is undermined by
the fact that other tasks, such as the task involving eating radishes or chocolates, allowed
participants only five minutes to consume as much of their assigned food as they wanted
27
(as long as they consumed either three radishes or three chocolates). Second, it is
possible that participants in the original study edited for a longer period of time than
participants in the present study. This also seems unlikely given the time limits used for
two other manipulations; specifically, participants in the chocolates and radishes
condition ate for five minutes and participants in the movie condition watched for ten
minutes. In addition, all of the experiments in the original study were completed in thirty
minutes, which suggests that the editing task in the original study could not have lasted
much longer than seven minutes.
Efforts to evaluate the effectiveness of the ego-depletion manipulations can be
frustrating due to the dearth of information reported in the original articles. Details such
as the amount of radishes or chocolates consumed or the amount of time participants
spent on the editing task are not reported. Additionally, there is no standardized
manuscript for the editing task (R. F. Baumeister, 2005, personal correspondence) and so
it is impossible to evaluate whether there is a specific effect of the manuscript used. To
their credit, the authors note that regarding the ego, they “do not have a clear
understanding of the nature of this resource” (Baumeister et al., 1998, p. 1263). One
consequence of this uncertainty is the difficulty in distinguishing whether a non-
significant finding, such as the present study, represents the failure to manipulate ego-
depletion or the lack of an effect of ego-depletion.
Gender and Temporal Discounting
The driving force behind group differences in this study is clearly gender. It is
important to note that no significant gender differences appeared in either the self-control
28
or impulsivity measures. Thus, the difference in discounting rates between males and
females is not reflected in the state or trait measures of either self-control or impulsivity.
Finding so clearly that men discount more steeply than women stands out against
most temporal discounting reports (e.g., Alessi & Petry, 2003; Kollins, 2003), but there
have been similar findings. Kirby and Marakovic (1996) found that men discounted
delayed rewards more steeply than women but only when real rewards, as opposed to
hypothetical rewards, were used. Read and Read (2004), however, found that men did
discount more steeply than women when hypothetical rewards were utilized. Bjorklund
and Kipp (1996) theorized that evolutionary processes might have pressured women to
develop stronger abilities to delay gratification than men, and Silverman (2003) explored
this hypothesis in a meta-analysis of thirty-three studies exploring gender differences and
the delay of gratification. Across a variety of studies women marginally delayed
gratification more than men (r2 = .058). This study, therefore, joins a small body of
research that indicates that men devalue delayed rewards more steeply than women do.
It is tempting to state that men discount more steeply than women because men
are more impulsive than women. The results of this study, however, do not support this
hypothesis. In terms of impulsivity as measured by the BIS-11, males’ scores (M =
63.21, SEM = 1.36) and females’ scores (M = 62.34, SEM = 1.61) did not differ
significantly,
t(80) = .407, p = .685). Thus, differences in trait impulsivity do not explain differences in
discounting rates between the genders. Additional research will be necessary to
characterize this difference.
29
This study also failed to replicate previous findings that higher impulsivity as
measured by the BIS-11 would be associated with larger K-values. It is important to note
that in Hinson et al.’s (2003) study, the researchers pretested the participants on the BIS-
11 and invited only participants from the highest quartile and lowest quartile to
participate. Thus, the BIS-11 might only be capable of predicting differences in K-values
between more extreme groups. Other researchers have similarly been unable to replicate
temporal discounting findings when they have used less extreme groups in the replication
than were used in the original study (e.g., Holt, Green, & Myerson, 2003).
The purpose of this study was to illuminate a relationship between temporal
discounting and ego-depletion by extrapolating from the working memory literature.
There was a non-significant trend in our findings in the direction of the hypothesis;
however, given that none of the manipulation checks found an effect, it is difficult to
conclude that ego-depletion had an effect on temporal discounting. Future research,
perhaps utilizing other, more powerful ego-depletion methods, may yet find evidence for
a central cognitive resource that can be temporarily exhausted leading to more impulsive
decision-making.
30
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33
Appendix A The Self-Control Scale
RB Scale
Using the scale provided, please indicate how much each of the following statements
reflects how you typically are (circle the number).
1. I am good at resisting temptation.2. I have a hard time breaking bad habits.3. I am lazy4. I say inappropriate things.5. I never allow myself to lose control.6. I do certain things that are bad for me, if they are fun.7. People can count on me to keep on schedule.8. Getting up in the morning is hard for me.9. I have trouble saying no.10. I change my mind fairly often.11. I blurt out whatever is on my mind.12. People would describe me as impulsive.13. I refuse things that are bad for me.14. I spend too much money.15. I keep everything neat.16. I am self-indulgent at times.17. I wish I had more self-discipline.18. I am reliable.19. I get carried away by my feelings.20. I do many things on the spur of the moment.21. I don’t keep secrets very well.22. People would say that I have iron self-discipline.23. I have worked or studied all night at the last minute.24. I’m not easily discouraged.25. I’d be better off if I stopped to think before acting.26. I engage in healthy practices.27. I eat healthy foods.28. Pleasure and fun sometimes keep me from getting work
done.29. I have trouble concentrating.30. I am able to work effectively toward long-term goals.31. Sometimes I can’t stop myself from doing something,
even if I know it is wrong.32. I often act without thinking through all the alternatives.33. I lose my temper too easily.34. I often interrupt people.35. I sometimes drink or use drugs to excess.36. I am always on time.
Not at all Very much 1------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------5
1------2------3------4------51------2------3------4------51------2------3------4------5
1------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------51------2------3------4------5
34
35
36
Appendix B The Barratt Impulsivity Scale (BIS-11)
Barratt ISRead each statement and check the appropriate space on the right side of the page. Do not spend too much
time on any statement. Answer quickly and honestly.
Rarely/Never Occasionally Often Almost always/always
1. I plan tasks carefully2. I do things without thinking.3. I make up my mind quickly.4. I am happy-go-lucky.5. I don’t “pay attention.”6. I have “racing” thoughts.7. I plan trips well ahead of
time.8. I am self-controlled.9. I concentrate easily.10. I save regularly.11. I “squirm” at plays or
lectures.12. I am a careful thinker.13. I plan for job security.14. I say things without thinking.15. I like to think about complex
problems.16. I change jobs.17. I act “on impulse.”18. I get bored easily when solving
thought problems.19. I act on the spur of the moment.20. I am a steady thinker21. I change residences.22. I buy things on impulse.23. I can only think about one
problem at a time.24. I change hobbies.25. I spend or charge more than I
earn.26. I often have extraneous thoughts
when thinking.27. I am more interested in the
present than the future.28. I am restless at the theatre or
lectures.29. I like puzzles.30. I am future oriented.
(__)(__)(__)(__)(__)(__)(__)(__)(__)(__)(__)(__)(__)(__)
(__)(__)(__)
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(__)
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(__)(__)(__)
(__)(__)(__)(__)(__)
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37
Appendix C Six BIS-11 subscales.
Factor 1: Attention 11. I “squirm” at plays or lectures.
28. I am restless at the theater or lectures. 5. I don’t “pay attention.” 9. I concentrate easily.* 20. I am a steady thinker. *
Factor 2: Motor impulsiveness 17. I act “on impulse.” 19. I act on the spur of the moment. 22. I buy things on impulse. 3. I make up my mind quickly. 2. I do things without thinking.
25. I spend or charge more than I earn. 4. I am happy-go-lucky.
Factor 3: Self-control 12. I am a careful thinker. * 1. I plan tasks carefully. * 8. I am self-controlled. *
7. I plan trips well ahead of time. * 13. I plan for job security.* 14. I say things without thinking.
* Indicates reverse scoring.
Factor 4: Cognitive complexity15. I like to think about complex problems. *
29. I like puzzles. 10. I save regularly.
27. I am more interested in the present than the future.18. I get easily bored when solving thought problems.
Factor 5: Perseverance 21. I change residences. 16. I change jobs. 30. I am future oriented. *
23. I can only think about one problem at a time.
Factor 6: Cognitive instability26. I often have extraneous thoughts when thinking. 6. I have “racing thoughts.”24. I change hobbies.
Appendix D The Momentary Impulsivity Scale
Part:
Condition: _________
Self Description -- How accurately do these words describe how you feel right now?
Please use this list of common human traits to describe how you feel right now compared to how you usually feel. Again, describe how you feel RIGHT NOW. Describe yourself as you feel currently, as compared with how you feel generally.
Before each feeling, please write a number indicating how accurately that trait describes how you feel right now compared to how you usually feel, using the following rating scale:
Less than usual More than usual________________________________________________________________________Extremely Very Quite Slightly Average Slightly Quite Very Extremely 1 2 3 4 5 6 7 8 9
________Creative
________Self-Controlled
________Sympathetic
________Impulsive
________Organized
Appendix E The Incidental Memory Task (answers in parentheses)
Participant number: _______
Age:______
Ethnicity: (circle one)
African-American Caucasian Hispanic Asian-American Other
How many speakers (excluding the intercom) were on the table? ______(Two)____
How many lamps were in the room? ______(One)____
What letters were printed on the lower left corner of the screen? ______(CMX)__
What color was the chair? ______(Blue)___
What was the background color on the monitor during the choices task?
______(Blue)__
Did the room have a fire alarm? ______(Yes)___
What color was the text during the discounting task? ______(Yellow)_
Was there a computer mouse on the table? ______(Yes)___
How many pens were on the desk? ______(Three)__
How many paper clips were on the desk? ______(None)__
Appendix F. Essay utilized in the ego-depletion task.Comparing the Use of Spatio-temporal Metaphors in Mandarin and English Speakers
The purpose of this paper is to propose a study comparing the use of spatio-temporal metaphors between English-speaking and Mandarin-
speaking samples. A recent article in the New York Times observed that Asian countries have made more scientific advancements in recent
years than America has (Broad, 2004). This observation raises the question of the role of language in science. Specifically, scientific
advancement depends on a language’s ability to provide metaphors for abstract concepts such as electricity and gravity and then to allow for the
linguistic manipulation of these metaphors (Gentner, Bowdle, Wolff, & Boronat, 2001). In examining differences in intellectual abilities between
American and Chinese samples, researchers have noted that Mandarin promotes skills in mathematics, which facilitates higher math scores in
Chinese populations (e.g., Stigler, Lee & Stevenson, 1986). Languages might also promote different understandings of abstract concepts such as
time. This paper will first review research into Mandarin, then examine research into spatio-temporal metaphors, and finally propose a study to
compare the spatio-temporal metaphors utilized by Mandarin-speaking and English-speaking populations. Examining these linguistic differences
reveals a number of insights into Chinese culture and language.
Chinese language Buttery and Leung (1998) noted that China is “a giant,” a rapidly developing country possessing one-fifth of the world’s
consumers who import $336 billion dollars (p. 375). The researchers noted many cultural differences between the America and China that create
difficulties in communication, particularly for businesses. One example of is the higher mean scores in Time Orientation found in Chinese
populations compared to American populations (Buttery & Leung, 1998). The researchers also noted well-established cultural differences such
as the more pronounced collectivism, the stronger uncertainty avoidance, and the more universal acceptance of unequal power distribution in
Chinese culture. Researchers have explored the theory that differences between languages might explain these and other differences between
Chinese and American populations. Stigler, Lee and Stevenson (1986) explored the idea that differences in mathematic abilities between Asian
and American students might be attributable, in part, to linguistic differences. In their study, they found that Chinese students were able to
remember significantly more numeric digits than American students. A subsequent study demonstrated that this difference was not due to
grouping strategies as both groups benefited equally from memory strategies when they were presented. The benefit was also not attributable to
the Chinese counting system, which emphasizes order and sequence of numbers (e.g., twenty-one in Mandarin is counted as two-ten-one).
Japanese utilizes the same system and the Japanese students in the study did not outperform Americans. There was also evidence that Chinese
children were not utilizing memory strategies more successfully in that American children outperformed the Chinese children on backward digit-
span tasks. Previous researchers theorized that short-term memory is not limited by a specified number of “chunks” but rather by the amount of
time necessary to pronounce words. Following this theory, the researchers examined the amount of time taken to pronounce Chinese numbers.
The amount of time necessary to pronounce Chinese numbers is significantly shorter than the amount of time necessary to pronounce American
or Japanese numbers. The researchers concluded that part of China’s advantage in mathematics is due to the speed with which the numeric
characters can be pronounced and not the speed with which phonemes are added to the articulation mechanism. Other researchers have also
argued that the use of numbers to described months (e.g. “six month” instead of “June”) provides Chinese students with increased familiarity with
the numeric system (Zhang & Zhou, 2003).
There has other been evidence demonstrating the influence of language on the basic perception of stimuli. Tse and Cavanagh (2000) asked
participants to observe the drawing of a Chinese character (which primarily resembled a backward “E”) on a computer screen. When
participants arrived, the complete character was pictured on the screen. If drawn, the character would be completed in six brush strokes, with
the last stroke beginning in the lower left of the area of the screen and connecting to the figure at the lower right area of the screen (completing
the backwards “E”). In this experiment, participants focused on a point in the lower portion of the screen while the six strokes each appeared
in their entirety; no animation or motion was involved. Four of the seven Chinese participants, who were familiar with the character, reported
seeing the left-to-right motion that would normally complete the character. All seven Americans, who were not familiar with the character,
reported seeing a right-to-left motion, which conforms to grouping processes in perception. Chinese language is also replete with idiomatic
expressions (Clements, 2001). Implicit, culturally held beliefs could be reflected through common figurative expressions
Appendix G An example of the stimuli with $1000 in one year as the delayed value; in
the ascending round, the hypothetical participant chooses the delayed value until $500 is
offered, and in the descending round, the participant chooses the immediate value until
$450 is offered. The averaged K-value for the participant in this round would be $475.
Ascending Round: Descending Round:
$1000 in One Year
$1000 NOW
$1000 in One Year
$990NOW
$1000 in One Year
$980NOW
$1000 in One Year
$500NOW
$1000 in One Year
$1NOW
$1000 in One Year
$5NOW
$1000 in One Year
$10NOW
$1000 in One Year
$450NOW
Appendix H Data recording sheets for each participant.
Date ______________________
Participant #________________________
Condition: A B
ASCENDING
Delay 1 wk 1 mth 3 mth 6 mth 1 yr 3 yrs 5 yrsPreferenceSwitch
DESCENDING
Delay 1 wk 1 mth 3 mth 6 mth 1 yr 3 yrs 5 yrsPreferenceSwitch
AVERAGED VALUES
Delay 1 wk 1 mth 3 mth 6 mth 1 yr 3 yrs 5 yrsAveraged Values
Appendix I Participants’ gender (male or female), ego-depletion condition (L = low
and H = high), average discounted value at each delay, K-value, transformed K-value (log
K+1), and R2 with all participants included
Part. Discounted Value by Delay Summary Values# Sex Cond Wk 1 1 Mth 3 Mth 6 Mth 1 Yr 3 Yr 5 Yr K Log (K
+ 1) R2
2 M L 990 875 475 300 500 300 200 .0336 .0144 .788 M L 775 675 575 575 525 475 375 .0034 .0015 .8015 M L 995 950 800 875 875 875 775 .0006 .0003 .3817 M L 875 875 775 650 500 500 500 .0043 .0019 .7121 M L 995 900 525 250 225 100 90 .0816 .0341 .9926 M L 995 995 775 550 475 225 175 .0234 .0100 .9930 M L 920 860 725 700 675 625 625 .0017 .0007 .5837 M L 950 910 875 775 725 475 475 .0049 .0021 .9638 M L 950 775 600 475 425 275 275 .0185 .0080 .8945 M L 875 825 675 475 475 475 475 .0046 .0020 .5349 M L 940 930 875 775 575 475 475 .0057 .0025 .8850 M L 995 995 940 910 910 875 995 .0000 .0000 .0054 M L 500 475 375 375 275 175 125 .0121 .0052 .9659 M L 900 850 775 575 475 325 275 .0130 .0056 .9761 M L 995 995 995 825 500 450 375 .0094 .0041 .8966 M L 930 725 625 675 650 450 275 .0060 .0026 .8468 M L 950 775 175 200 30 30 8 .2273 .0890 .9469 M L 985 980 930 930 930 875 875 .0005 .0002 .7677 M L 995 875 900 875 725 475 375 .0060 .0026 .9681 M L 725 325 125 90 50 5 5 .6515 .2179 .9983 M L 995 875 475 275 90 90 90 .1025 .0424 .985 M H 995 825 775 750 700 575 600 .0024 .0010 .707 M H 960 525 525 400 200 90 90 .0562 .0237 .8813 M H 225 245 95 60 15 15 7.50 .1093 .0450 .9219 M H 995 875 875 875 700 675 850 .0007 .0003 .1823 M H 995 985 875 775 725 475 275 .0081 .0035 .9928 M H 700 925 950 950 850 775 650 .0011 .0005 .4135 M H 475 450 200 175 90 90 90 .0758 .0317 .9040 M H 275 100 90 50 50 50 50 .3992 .1459 .7941 M H 995 775 475 275 275 275 175 .0651 .0274 .8947 M H 995 995 995 985 985 940 875 .0005 .0002 .9752 M H 950 875 875 525 500 375 275 .0137 .0059 .9356 M H 950 900 850 700 625 500 450 .0054 .0023 .9257 M H 775 400 325 225 90 90 90 .1459 .0591 .9162 M H 650 525 300 250 100 50 50 .0840 .0350 .9764 M H 985 985 1000 725 475 225 125 .0188 .0081 .9665 M H 775 675 275 225 175 90 90 .1041 .0430 .9567 M H 875 900 910 850 825 725 650 .0015 .0007 .9870 M H 950 850 800 750 675 675 475 .0029 .0013 .8471 M H 960 475 475 375 250 175 90 .0507 .0215 .8180 M H 940 875 850 700 675 450 350 .0068 .0029 .9985 M H 995 960 910 875 875 825 775 .0009 .0004 .8387 M H 950 875 675 600 325 175 115 .0274 .0117 .971 F L 725 550 350 265 220 60 60 .0638 .0269 .974 F L 995 905 875 850 800 775 775 .0009 .0004 .529 F L 975 985 875 875 775 500 375 .0059 .0026 .98
Part Discounted Value by Delay Summary Values# Sex Cond Wk 1 1 Mth 3 Mth 6 Mth 1 Yr 3 Yr 5 Yr K Log (K +
1) R2
12 F L 995 970 970 930 875 775 675 .0018 .0008 .9914 F L 950 960 770 795 600 475 375 .0067 .0029 .9218 F L 960 910 920 850 850 800 700 .0012 .0005 .9122 F L 875 800 125 225 175 225 75 .1607 .0647 .8129 F L 995 950 875 825 775 675 575 .0027 .0012 .9332 F L 995 875 625 625 625 625 625 .0017 .0007 .2833 F L 995 995 995 995 995 995 995 .0000 .0000 1.0039 F L 625 575 625 475 425 275 150 .0094 .0041 .9742 F L 995 990 990 775 775 725 725 .0071 .0031 .6444 F L 995 950 875 875 875 825 725 .0011 .0005 .8346 F L 800 650 625 575 625 625 575 .0007 .0003 .2553 F L 875 775 475 475 625 90 100 .0195 .0084 .8258 F L 995 900 800 910 700 475 475 .0048 .0021 .8763 F L 950 750 600 550 475 450 400 .0060 .0026 .6572 F L 875 885 750 650 475 425 300 .0092 .0040 .9375 F L 675 400 325 275 250 175 175 .0253 .0109 .7176 F L 995 995 985 875 875 775 775 .0013 .0006 .8382 F L 875 675 625 650 725 650 625 .0007 .0003 .2086 F L 950 875 775 625 575 500 475 .0050 .0022 .793 F H 970 875 775 675 525 400 375 .0088 .0038 .926 F H 995 995 900 825 825 825 675 .0015 .0007 .7610 F H 875 575 375 300 375 225 100 .0390 .0166 .8011 F H 995 995 995 995 995 995 995 .0000 .0000 1.0016 F H 995 940 875 875 825 775 675 .0015 .0007 .8820 F H 960 925 800 600 575 575 425 .0053 .0023 .7724 F H 875 825 725 675 525 475 425 .0050 .0022 .8525 F H 950 950 950 905 875 775 725 .0013 .0006 .9827 F H 750 600 475 400 475 400 300 .0048 .0021 .6331 F H 970 960 960 930 900 800 550 .0023 .0010 .9234 F H 875 475 475 475 475 475 475 .0014 .0006 .1336 F H 960 960 920 875 800 675 525 .0031 .0013 .9943 F H 995 900 825 575 575 300 300 .0137 .0059 .9748 F H 990 995 995 995 975 800 775 .0013 .0006 .9351 F H 550 475 475 425 375 300 300 .0037 .0016 .8655 F H 970 950 910 875 875 875 825 .0005 .0002 .6760 F H 970 970 970 875 930 825 725 .0012 .0005 .9373 F H 995 940 775 995 875 950 970 -.0002 -.0001 .0774 F H 995 995 995 800 775 475 475 .0058 .0025 .9678 F H 775 825 675 350 700 200 225 .0127 .0055 .7779 F H 970 960 950 910 885 850 475 .0025 .0011 .8084 F H 995 995 995 995 995 970 970 .0001 .0000 .87
M 896.95 814.2 709.3 637.8 586.3 490.8 437.4 .0327 .0127 .80S. D. 155.2 200.2 253.9 263.2 273.3 282.8 280.6 .0879 .0311 .23
SCHOLASTIC VITAE
CODY B. COX
BORN: January, 24, 1978, Waco, Texas
UNDERGRADUATE STUDY: Southwestern UniversityGeorgetown, TXB.A., Psychology, 2000B.A. Religion, with Honors, 2000
GRADUATE STUDY: Wake Forest UniversityWinston-Salem, NC
M.A., Experimental Psychology, 2005Thesis Title: Examining the Effects of
Ego-Depletion on Temporal Discounting
SCHOLASTIC AND PROFESSIONAL EXPERIENCE:
2004 Wake Forest University Summer Research Fellowship2003-2005 Wake Forest University Graduate Assistantship2000 Psi Chi / Allyn & Bacon Psychology Award for Writing (3rd place)2000 Norman M. Spellman Award, Outstanding Student in Religion
PROFESSIONAL SOCIETIES
1999-2000 Psi Chi, Psychology National Honor Society (Treasurer, 1999-2000)
PUBLICATIONS AND PRESENTATIONS
Cox, C. B., & Giuliano, T. (1999). Constructing obstacles versus making excuses: Examining perceivers’ reaction to behavioral and self-reported self-handicapping. Journal of Social Behavior and Personality, 14, 419-432.
Cox, C. B., & Beck, R. C. (2005). Examing the effects of mental imagery on temporal discounting. Poster presented at the North Carolina Cognition Conference, Winston-Salem, N.C.
Cox, C. B. (2002, October). Copping out: Exploring perceivers’ reactions to behavioral and self-reported self-handicapping. In T. A. Giuliano (Chair), Working out, copping out, stressing out: Reviewing and reflecting on three student research projects conducted in Traci Giuliano’s psychology lab. Symposium conducted at Southwestern University’s Alumni University, Georgetown.
Cox, C. B., Patrick, E. C., Barrera, P. V., & Giuliano, T. A. (1999). Nothing ventured, nothing lost: Perceptions of behavioral vs. self-reported self-handicapping. Paper presented at the 45th annual meeting of the Southwestern Psychological Association, Albuquerque, NM.
