THE EFFECTS OF PRESENTATION AND PROCESSING ON EXPLICIT MEMORY

IN OLDER ADULTS

A Thesis

Presented to the faculty of the Department of Psychology

California State University, Sacramento

Submitted in partial satisfaction of

the requirements for the degree of

MASTER OF ARTS

in

Psychology

by

Felicia Elena Luz Oropeza

SPRING

2012

ii

THE EFFECTS OF PRESENTATION AND PROCESSING ON EXPLICIT MEMORY

IN OLDER ADULTS

A Thesis

by

Felicia Elena Luz Oropeza

Approved by:

__________________________________, Committee Chair

Kelly Cotter, Ph.D.

__________________________________, Second Reader

John Schaeuble, Ph.D.

__________________________________, Third Reader

Emily Wickelgren, Ph.D.

____________________________

Date

iii

Student: Felicia Elena Luz Oropeza

I certify that this student has met the requirements for format contained in the University

format manual, and that this thesis is suitable for shelving in the Library and credit is to

be awarded for the thesis.

__________________________, Graduate Coordinator ___________________

Jianjian Qin, Ph. D. Date

Department of Psychology

iv

Abstract

of

THE EFFECTS OF PRESENTATION AND PROCESSING ON EXPLICIT MEMORY

IN OLDER ADULTS

by

Felicia Elena Luz Oropeza

Forty eight older adults, sampled from two senior communities, watched a series of

words on a computer monitor and then took a written exam that tested their explicit word

recall. Results revealed a main effect for presentation, such that participants correctly

recalled more words when those words were presented for 2 seconds than when those

words were presented for .04 seconds. Results also revealed an interaction between

presentation and processing, where the supraliminal presentation yielded more correctly

recalled words in thematic conditions than in non-thematic conditions. These results

suggest that older adults exhibit higher explicit memory performance when words

belonging to a theme or category are presented within conscious awareness than outside

awareness, likely because they are able to process the information more deeply.

_______________________, Committee Chair

Kelly Cotter, Ph.D.

_______________________

Date

v

DEDICATION

I would like to dedicate this thesis to my deceased maternal grandparents, Maria

de la Luz Razo and Salvador Gomez who raised me and served as the inspiration for my

topic on cognition and aging.

vi

ACKNOWLEDGMENTS

First and foremost, I would like to thank my parents for everything they have

done for me. Since preschool, my parents have impressed upon me the value of education

and importance of using one’s intellect to make a significant impact on the world;

however small or big that may be. They gave me the greatest gift that any parent could

bestow on their child, individuation, by giving me the freedom to explore my academic

pursuits. My thesis topic availed me this golden opportunity to spread my wings and fly.

Special thanks to my mother’s extended family for their undying support of my

educational endeavors and contributions to my personal development throughout

graduate school. During graduate school, my grandmother passed away which was a

major setback for our family, for she was the anchor that held our family together.

Amidst those trying times, my mom’s family taught me to rise above hardships and to

find my inner strength within to finish my degree. I would like to thank Dr. Kelly Cotter

for her patience, immense wisdom, alacrity, and generosity of time and effort towards

helping me finish my thesis. I would also like to thank Dr. John Schaeuble for helping me

arrive at my thesis topic and for assisting me with narrowing my thesis topic down to two

variables. I would like to thank Dr. Wickelgren for helping me with the Latin Square

Experimental Design of my video presentations to eliminate bias. I would like to thank

Debbie Kircher for pacing me through the program and helping me see my own beauty

within.

vii

TABLE OF CONTENTS

Dedication ............................................................................................................................v

Acknowledgements ............................................................................................................ vi

List of Tables ..................................................................................................................... ix

List of Figures ......................................................................................................................x

Chapter

1. INTRODUCTION ........................................................................................................1

Memory ....................................................................................................................1

Supraliminal and Subliminal Memory Processes ....................................................3

Levels of Processing ................................................................................................4

Interaction of Levels of Processing and Timing of Presentation .............................5

The Present Study ....................................................................................................6

2. METHOD .....................................................................................................................8

Materials ................................................................................................................10

Participants .............................................................................................................13

Procedure ...............................................................................................................13

3. RESULTS ...................................................................................................................16

Hits .........................................................................................................................17

False Alarms ..........................................................................................................19

4. DISCUSSION ............................................................................................................20

Strengths and Limitations ......................................................................................23

viii

Future Directions ...................................................................................................28

Conclusion .............................................................................................................29

Appendix Final List of Forty Words Used in the Four Video Conditions ...................30

References ........................................................................................................................31

ix

LIST OF TABLES

Tables Page

1. Descriptive Statistics for Hits and False Alarms ....................................................... 16

x

LIST OF FIGURES

Figures Page

1. The Interaction of Presentation and Relatedness for Hits ..............................................18

2. The Main Effect of Presentation for False Alarms ........................................................19

1

Chapter 1

INTRODUCTION

Dementia is a degenerative disease of the aging brain that impairs cognitive

functioning by attacking the central nervous system at the vascular and cellular levels

(Whitehouse, Price, Strubie, Clark, Coyle, & Delon, 1982). A reputable occupational

health and medical disability advisory website, MDGuidelines, provides the article

“Dementia definition” (2009) stating that although dementia impairs cognitive

functioning in many ways, profound and irreversible memory loss is its primary effect.

Because dementia is an increasingly prevalent age-related neural disease within senior

populations, developing cognitive strategies for preventing memory loss is necessary for

maintenance of quality of life and positive life orientations (Santacruz & Swagerty,

2001). I focus on two potential memory-enhancing strategies in the present study:

presentation of information and processing of information. I examine these strategies as

employed by older adults who do not suffer from cognitive impairment, in hopes that

what is learned in normal aging populations can be beneficial for those at risk of

developing dementia.

Memory

Memory, as defined in The American Heritage Dictionary (1985), is the act of

encoding, storing, and recalling a past event or item of factual knowledge. Memory can

be divided into two forms: implicit and explicit (Graf & Schacter, 1985), both of which

are affected by the aging process (Light & Singh, 1987). Implicit memory depends on

2

cognitive processes occurring outside of one’s conscious awareness (Schacter, 1987).

These automatic processes can include stimuli-associate conditioning, social modeling,

relearning and practice effects, and priming (Schacter, 1987). Roediger and McDermott

(1993) and Schacter (1987) described implicit memory tasks as indirect, where there was

no reference to past exposure to information.

In contrast, explicit memory tasks require the conscious recollection of an item

directly referenced by past experience (Graf & Schacter, 1985). When one performs well

on an explicit memory test, he or she has brought factual knowledge into awareness

(Challis, 1996; Joyce, Paller, McIsaac, & Kutas, 1998). Roediger and McDermott (1993)

and Schacter (1987) characterized explicit memory tests as tasks performed with

intention, where participants are instructed to recall or recognize stimuli they had

previously seen.

I chose to analyze free recall test performance as a measure of explicit memory

processes in the current study. Performance on a free recall exam is a direct measurement

of the conscious recollection of previously presented stimuli. This type of memory task

relies on processing capacity, revealing the influence of working memory and processing

speed on retrieval (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996; Whiting &

Smith, 1997). Free recall tests typically depend on effortful cognitive control and bottom

up retrieval processes.

In cross-sectional and longitudinal studies examining age-related memory, older

participants tend to score lower than younger participants on explicit memory tasks

(Anooshian, 1997; Carroll, Byrne, & Kirsner, 1985; Ellis, Ellis, & Hosey, 1993;

3

Greenbaum & Graf, 1989; Lorsbach & Morris, 1991; Lorsbach & Worman, 1990; Naito,

1990; Parkin & Streete, 1988). However, older cohorts show equal performance to young

adults on perceptual implicit tasks (Light & Singh, 1987) shedding light on potential

compensatory mechanisms used by older adults to preserve explicit memory. To

investigate the older cohorts’ adaptive use of cognitive tools further, I analyzed the

influence of two associative memory processes on explicit memory test performance in

older adults: level of processing (shallow versus deep) and awareness of presentation

(subliminal versus supraliminal), described in detail below.

Supraliminal and Subliminal Memory Processes

As described above, explicit memory tests often involve asking participants to

recall or recognize information presented to them in a laboratory setting. The information

can be presented supraliminally (within one's conscious awareness) or subliminally

(outside one's ability to consciously perceive presented stimuli) in the study/encoding

session. Supraliminal memory processes are driven by strong feelings of event

recollection that enhance one’s ability to visualize the scene (Aggleton & Brown, 1999;

Gardiner, 1988; Gardiner & Java, 1990; Gardiner & Java, 1991; Gardiner, Java &

Richardson-Klavehn, 1996; Jacoby, 1991; Rajaram, 1993; Tulving, 1985; Wagner,

Verfaeille, & Gabrieli, 1997; Yonelinas, 2002). Subliminal processes depend upon

feelings of familiarity that lack a concrete experience of an actual event (Khilstrom,

1990; Khilstrom, Barnhardt, & Tataryn, 1992a; Khilstrom, Shames, & Dorfman, 1996;

Roediger & McDermott, 1993; Szymanski & MacLeod, 1996; Toth, 1996). The priming

4

task is a classic methodology for studying subliminal processes (Kiefer, 2007). Age has

little effect on priming (Light & Singh, 1987).

Levels of Processing

Ritchey, Bessette-Symons, Hayes, and Cabeza (2011) showed that semantic

elaboration can enhance neural processing in the medial prefrontal cortices of the human

brain. Deep encoding requires the utilization of meaning-based encoding to activate

associative memory network connections, while shallow processing refers to the

presentation of stimuli encoded at a rudimentary or physical level without the use of

semantic-level memory access (Craik & Lockhart, 1972). For example, deep processing

is applied during exposure to a word list consisting of items belonging to the same

category, such as Zoo Animals, because people form associations between the words. On

the other hand, shallow processing is utilized during exposure to randomly chosen words

because there is no categorical link between the words. Craik and Lockhart (1972)

showed that deep or semantically-processed stimuli had a higher chance of being recalled

than shallow or physically-processed stimuli. This effect was found even when

participants did not expect subsequent recall or recognition tests.

Bradshaw and Anderson (1982) also showed the effect of elaboration and

thematic-relatedness on memory processes: Participants in their study demonstrated

higher memory performance in the thematic conditions, which required the elaborate

integration of memory traces, and lower memory performance in the conditions with

minimal thematic-relatedness. Similarly, levels of processing theory stipulates that

performance is facilitated by elaborately encoded or “deeply” processed stimuli and

5

degraded by low-level encoding or “shallow” processing of stimuli (Craik & Lockhart,

1972). Hence, Bradshaw and Anderson’s (1982) study draws parallels between thematic-

relatedness and levels of processing theory, shedding light on the role of neural networks

in the creation of interconnected explicit memory traces. In the current study, I adapted

the methodology that used thematic-relatedness in order to operationally define levels of

processing.

Interaction of Levels of Processing and Timing of Presentation

Effortful processing may enhance memory performance in older cohorts on

priming tests. Englekamp and Wippich (1995) demonstrate an age effect for conceptual

priming, such that younger cohorts generally show higher memory on implicit tests than

older cohorts when presented with atypical stimuli at study. Englekamp and Wippich

showed that younger cohorts tend to perform better than older cohorts in random stimuli

and subliminal presentation conditions while performing worse in moderate-relatedness

conditions.

The distinction between the cognitive resources that drive explicit and implicit

memory processes begin to blur (Srinivas & Roediger, 1990) as category exemplar tasks

capture both conceptual subliminal processes and perceptual subliminal processes. While

unraveling the effects of conscious and unconscious processes on memory, Monti et al.

(1996) investigated how category exemplar tasks rely on relatedness to create meaning-

based or deeply processed memory traces. Although category exemplar tasks are

classically referred to as “implicit” memory tasks, their conceptual properties are

sensitive to different levels of processing at the supraliminal level (Monti et al., 1996).

6

Hence, category exemplar tests may have more conceptually-driven effects on memory if

coupled with deep levels of processing conditions. Therefore, among the memory tasks

available to researchers, the category exemplar test is one of the most effective priming

tools for studying the interaction of levels of processing and exposure to subliminal and

supraliminal stimuli (Mitchell & Bruss, 2003). Thus, in the present study I applied the

category exemplar test by presenting target exemplars from taxonomic groups of animals

and vegetables to the participants and by asking participants to recall those targets later.

Despite the potential interaction between processing and presentation, there

remains a paucity of research that examines the moderated effects of semantically

processed stimuli on category exemplar task performance in older adults. Thus, in

contrast to recent studies examining the relationship between relatedness, elaboration,

and explicit memory (Bradshaw & Anderson, 1982), I analyzed the effect of presentation

timing and thematic-relatedness on the explicit memory of older adults in the current

study.

The Present Study

In the present study, I examined how levels of processing (deep versus shallow)

affects explicit memory task performance when moderated by presentation timing

(subliminal versus supraliminal). I operationally defined deep processing as the

presentation of thematically-related words from two thematic categories (Zoo Animals

and Vegetables). I defined shallow processing as the presentation of randomly generated,

non-thematically-related words. I defined supraliminal presentation as seeing a series of

7

words for 2 seconds each. Subliminal presentation was defined as seeing a series of

words for .04 seconds each.

I expected to find main effects for both presentation and processing of stimuli. For

the main effect of presentation, I expected to see a higher number of supraliminally-

presented words recalled than subliminally-presented words. For the main effect of

relatedness, I proposed that memory for thematically-related words would be higher than

memory for non-thematically-related words. Specifically, I expected that thematically-

related words would provide a semantic (deep) form of processing that would facilitate

memory performance across both supraliminal and subliminal presentation conditions.

I also hypothesized that participants would have higher memory performance in

supraliminal-deep levels of processing conditions and lower performance in supraliminal-

shallow, subliminal-deep, and subliminal-shallow conditions. I expected to see this

interaction because meaningful, related words shown for a longer amount of time on a

computer screen tend to produce more durable memory traces than random words or

words presented for a shorter amount of time. The focusing of one’s mind on semantic

content should yield a compound effect on explicit memory performance because

supraliminal processes require the effortful application of cognitive resources that spark

neural network activation and parallel processing stream distribution.

8

Chapter 2

METHOD

With a 2x2x4 mixed repeated-measures factorial design, described in detail

below, I examined the nature of semantic facilitation on explicit memory for words

presented at the conscious and the unconscious perceptual level. I showed each

participant a series of forty words flashed on a computer screen and later asked

participants to recall the words. The two within-subjects independent variables were

thematic association of words and presentation of stimuli. The between-groups

independent variable was order of presentation. Explicit memory recall test performance

was my dependent variable.

The first within-subjects independent variable was thematic association/level of

processing. Thematic association referred to how easily participants could form

associations with presented words (thus affecting their memory for those words), and was

comprised of two levels: a thematically-related word condition (deep processing) and a

non-thematic word condition (shallow processing). The thematically-related word

condition was a list of ten words related to the same category, either Zoo Animals (e.g.,

zebra, kangaroo) or Vegetables (e.g., broccoli, potato). The non-thematic word condition

was a list of ten randomly generated words that had no relation to each other (e.g., skirt,

motorcycle).

The second within-subjects independent variable, presentation of stimuli, referred

to how long participants saw words flashed on the computer screen. This variable had

9

two levels: the supraliminal condition and the subliminal condition. In the supraliminal

condition, participants were exposed to words for 2 seconds each. This presentation time

was long enough for participants to read and understand the word, thus processing it

completely (Moore, 1982; Whiting, 1997). Words were presented for .04 seconds each in

the subliminal condition. This presentation time was long enough for participants to

detect a word, but not long enough to consciously process the word (Khilstrom, 1987;

Moore, 1982).

Video presentation, consisting of four levels, was the only between-subjects

variable used in this study. It was used in order to control for potential order effects. I

used a partial Latin-Square to counterbalance the sequence of phases within each video

presentation. This method of counterbalancing ensured that the thematic and non-

thematic words were presented in every possible order (first, second, third, fourth). For

example, order one consisted of supraliminal thematic words presented in phase 1,

subliminal non-thematic words presented in phase 2, supraliminal non-thematic words

presented in phase 3, and subliminal thematic words presented in phase 4. In order two,

by contrast, supraliminal non-thematic words appeared in phase 1, subliminal thematic

words appeared in phase 2, supraliminal thematic words appeared in phase 3, and

subliminal non-thematic words appeared in phase 4. (Each video started with a

supraliminal phase in order to prevent the participant from thinking that there were no

words presented in the video.) Thus, the presentation conditions were counterbalanced

across the four different videos. A total of forty words were presented in each video.

10

Materials

Word Generation

To create the vegetable word list I randomly selected 41 Vegetable words from

the following website: http://www.gardenology.org/wiki/List_of_vegetables. To create

the zoo animal word list I randomly selected 26 Zoo Animal words from the following

website: http://www.catalandictionary.org/wordnets/eng/ZooAnimalList.htm. To create

the non-thematic word list I randomly generated 24 words from the following website:

http://coyotecult.com/tools/randomwordgenerator.php. Next, I trimmed each list to 10

words following the procedures described below.

Inter-rater Reliability

The relatedness of a word to a category could affect the speed and accuracy by

which a participant could retrieve the word from memory, thus assisting in the formation

of cognitive associations (Anderson, 1980). Therefore, I wanted to make sure that one

word list did not contain words that were more related to their respective theme than the

other words to that list’s respective theme. To check the equivalence of thematic-

relatedness of the words in the two thematic word lists, I collected inter-rater reliability

data on the degree of relatedness of each word to its specific category.

Ten friends and family members below the age of 55 participated as raters. They

were asked to rate how much each word from the vegetable list was related to the theme

of vegetables, and how much each word from the zoo animals list was related to the

theme of zoo animals. Relatedness ratings were collected only for thematic words.

11

I also collected inter-rater reliability data on the commonness of each word in

everyday usage because the commonness of a word could also increase the accuracy of

recall (Deese, 1960; Gregg, Montgomery, & Castano, 1980; Hall, 1954; Matthews, 1966;

May, Cuddy, & Norton, 1979; May & Tryk, 1970; Postman, 1970; Sumby, 1963; Tulving

& Patkau, 1962; Whiting & Smith, 1997). The commonness inter-rater questionnaire

asked raters to rate how commonly words are used in everyday speech. Commonness

ratings were collected for thematic and non-thematic words. Upon completion of the

word rating procedure, I rewarded the raters with $5.00 Target gift cards.

Final Word List Creation

To create lists of equivalent length (10 words) for each processing condition

(thematically-related and non-thematically-related), I entered the participants’ ratings into

a spreadsheet. Next, I eliminated some words from the original lists by sorting the word

lists (Zoo Animals, Vegetables, non-thematic) from the highest to lowest mean

commonness rating. Then I chose every other two words descending from the highest to

lowest mean commonness rating until I obtained 20 words for each thematic list (Zoo

Animals, Vegetables) and 20 words for the non-thematic word lists. The final list of 40

words was divided into four lists of ten words each using the ABBA sorting sequence.

Refer to Appendix for the list of words used in the video conditions.

After the final word lists were created, I calculated the variability between the two

thematic word lists on relatedness and the variability between the two thematic and the

two non-thematic lists on commonness. T-tests revealed no significant differences

between Zoo Animal words (M = 4.09, SD = .54) and Vegetable words (M = 3.71, SD =

12

.76) on relatedness to their respective thematic category; t (38) = 1.73, p = .09. In other

words, Zoo Animal words and Vegetable words had the same degree of relatedness to

their respective theme. T-tests also showed no significant differences between thematic

(M = 3.49, SD = .63) and non-thematic words (M = 3.34, SD = 1.03) on commonness; t

(38) = .70, p = .48. Thus, both thematic and non-thematic words were considered

equivalent on commonness.

Upon completion of the word list generation procedure I had four lists of 10

words. These lists were capped at 10 words each because the average older adult has a

working memory capacity of 4 (+/- 2) items (Bo, Borza & Seidler, 2009). I chose to

increase the size of the word list from four words to ten words because I wanted to avoid

any potential ceiling effects (Miller, 1956).

Finally, to randomly sort the words within the four lists for the video presentation

conditions, I used the following website: http://textmechanic.com/Sort-Text-Lines.html,

which generated random orders for each 10-word list.

Computer

Words were presented to participants on an ASUS gaming laptop computer

running Windows Live Movie Maker for Windows 7 Home Premium operating system.

Demographic Questionnaire

Before administering the computerized portion of the procedure I collected the

following demographic information: Gender, Highest Education Achieved, Occupation,

Ethnicity, and Religion. Age information was not collected because my entire participant

13

pool consisted of older adults and I did not want the sensitivity of the age question to

deter potential subjects from participating in my study.

Participants

I sent letters to fourteen different agencies within the Sacramento Valley region

and called ten agencies. I recruited forty-eight older adults over the age of 55 from the

following agencies: Senior Center at Elk Grove, Mission Oaks/Swanston Community

Center in Carmichael, and Ethel Hart Senior Center. Of the twelve participants who

answered the question on “Gender,” 3 participants were “Male” and 9 participants were

“Female.” Four out of 48 participants “Completed High School,” 11 “Went to college but

did not finish,” 12 participants “Finished some graduate school or higher,” and 2 “Earned

a doctorate degree.” (The questionnaire did not include an option for those who

completed college but did not attend graduate school.) Almost half of the participants

were “Caucasian” (n = 23), 4 were “Hispanic,” 1 participant was of “Asian American”

descent, 2 were “African American,” and 18 did not indicate their ethnicity. Out of 45

participants who responded to the Religion question, 12 were “Catholic,” 13 were

“Christian,” 5 were “Spiritual,” 1 was “Mormon,” 1 was “Episcopalian,” 3 participants

were “Atheist,” 3 were “New Age,” 2 were “Baptist,” and 5 participants reported “Other”

to signify that they were of a religious affiliation other than what was asked on the

questionnaire. Three participants out of 48 did not respond to the religion question.

Procedure

I received approval at minimal risk to recruit participants from the Human

Subjects Committee in the Department of Psychology in Spring 2011. Next, I pilot-tested

14

the procedure with four individuals who did not meet the study’s criteria for participation

to make sure the testing protocols ran smoothly. There were no problems with the

procedure.

To prepare for the experiment, I made arrangements with the activity coordinators

from each agency listed above to secure a room and a specific time to run my study.

Before the day of the experiment, I randomly assigned the participants to one of four

video conditions. On test day, I greeted each participant individually, showed the

participant to his or her seat in front of the laptop, and led the participant through the

informed consent procedure. Next, I handed the participant a consent form to sign and

return back to me. I then provided the participant with a demographic questionnaire that

asked the participant to reveal his or her gender, education status, occupation, religion,

and ethnicity.

Before starting the video presentation, I instructed the participant to not touch any

key on the keyboard or touchpad because the screen ran by itself. Next, I started the video

assigned to the participant. Within each video, the supraliminal condition had one

thematic phase and one non-thematic phase. The subliminal condition also had one

thematic phase and one non-thematic phase. The order was counterbalanced, as described

above.

The video presentation lasted for 3.99 minutes. In the supraliminal condition, a

blank screen appeared first for 1 second. The orienting stimulus, "_ _ _ _ _ _ _ _ _ _ ",

flashed for .5 seconds before each word appeared on the screen. The masking stimulus,

"XXXXXXXXXX", followed each word and remained on the screen for .5 seconds. A

15

blank screen appeared for 1 second before the orienting stimulus for the next word. In the

subliminal condition the blank screen was shown for 2 seconds before the appearance of

the next word. The orienting stimulus, "_ _ _ _ _ _ _ _ _ _", flashed for .5 seconds before

each word and the masking stimulus, "XXXXXXXXXX", appeared on the screen for a

duration of .5 seconds after the flashing of each word. A blank screen appeared for 2

seconds before the orienting stimulus for the next word. The difference in timing of the

presentation of blank screens was potentially problematic but unequal durations for the

four videos would have compromised the internal validity of my repeated measures

design. To ensure that each video condition lasted for an equivalent amount of time, I

prioritized consistency of video presentation length across my video conditions over

equal time spacing between orienting stimuli, test words, and masking stimuli.

After the video was complete, I administered the free recall exam by giving the

participant a pen and piece of lined 8.5 x11 white printer paper with the following

instructions at the top of the page: “Please write as many words as you can remember from

the presentation you just saw. You have as much time as you want to complete this form.”

Next, I told the participant that he or she could take as much time as needed to complete

the test. After I read the instructions to the participant, I quietly left the room. After the

exam was complete, I debriefed the participant and gave the participant a $5 gift card to

Walmart.

16

Chapter 3

RESULTS

Using two mixed repeated measures ANOVAs, I examined differences between

the thematic and presentation conditions on word recall (see Table 1).

The first dependent variable, the number of “hits,” represented the number of

words the participant wrote down on the recall task that were presented in the video

presentation (i.e., correctly-recalled words). The second dependent variable, number of

Table 1

Descriptive Statistics for Hits and False Alarms (N = 48)

Hits False Alarms

Source M SD F(1, 44) p

M SD F(1, 44) p

Relatedness

100.37 < .001 .19 .67

Thematic 2.13 0.13 0.10 0.04

Non-thematic 0.57 0.11 0.13 0.05

Presentation 220.90 < .001 10.05 .003

Supraliminal 2.63 0.17 0.22 0.06

Subliminal 0.07 0.05 0.01 0.01

Relatedness x Presentation 109.13 < .001 0.00 1.00

Thematic Supraliminal 4.10 0.23 0.21 0.07

Thematic Subliminal 0.15 0.09 0.00 0.00

Nonthematic Supraliminal 1.15 0.21 0.23 0.09

Nonthematic Subliminal 0.00 0.00 0.02 0.02

17

false alarms, was the number of words that the participant wrote down on the recall task

that were not presented in the video presentation. I associated each false alarm with the

condition that contained a structurally similar word. For example, if one condition

contained the word ”torchlight” and the participant wrote the word “headlight,” I placed

the false alarm score in the condition that contained “torchlight.”

Hits

The between subjects variable, presentation order, did not show a significant main

effect for hits, F (3, 44) = 2.18, p = .10, indicating that order of presentation had no effect

on correct recall for presented words. Additionally, there were no significant two-way or

three-way interactions with presentation order for hits. The first within-subjects variable,

timing of presentation, showed a significant main effect for hits, F (1, 44) = 220.90, p <

.001, semi-partial η2 = .46, such that supraliminal presentation conditions yielded a higher

number of hits than subliminal presentation conditions, as predicted (see Table 1).

However, the presence of an interaction modified the nature of this main effect. The

second independent variable, thematic-relatedness, also showed a significant main effect

for hits, F (1, 44) = 100.37, p < .001, semi-partial η2

= .17, such that thematic conditions

produced significantly more hits than non-thematic conditions. However, the interaction

showed that this effect did not exist for the subliminal condition.

Both main effects had to be viewed in the context of a significant interaction, F

(1, 44) = 109.13, p < .001, semi-partial η2

= .14. Pairwise comparisons were used to test

for simple effects of the thematic conditions. For supraliminal presentation conditions

there was a significant mean difference between thematic and non-thematic conditions

18

such that the number of hits in thematic conditions was significantly higher than the

number of hits in non-thematic conditions, Mean difference = 2.96, p < .001. However,

there was no difference between the two thematic conditions in the subliminal condition,

Mean difference = .15, p =.11.

Figure 1. The interaction of presentation and relatedness for hits.

4.10

1.15

0.15 0.00 0.00

1.00

2.00

3.00

4.00

5.00

6.00

Thematic Non Thematic

Per

form

an

ce

Relatedness

Supraliminal

Subliminal

Presentation

19

False Alarms

The between subjects variable, presentation order, did not show a significant main

effect for false alarms, F (3, 44) = .60, p = .62, revealing no effect of video order on the

number of written responses that were not on the word list but resembled words on the

list. Moreover, there were no significant two-way or three way interactions with

presentation order for false alarms. Presentation showed a significant main effect for

false alarms, F (1, 44) = 10.05, p < .001, semi-partial η2 = .10, such that there were

more false alarms produced in supraliminal presentation conditions than in subliminal

presentation conditions (see Table 1). However, thematic-relatedness did not show a

main effect for false alarms, F (1, 44) = .19, p = .67. Similarly, there was no interaction

of presentation and thematic-relatedness, F (1, 44) = .00, p = 1.00, for false alarms. See

Figure 2 for the main effect of presentation time on false alarms.

Figure 2. The main effect of presentation for false alarms.

0.21

0.23

0 0.02

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Thematic Non Thematic

Supraliminal

Subliminal

Relatedness

P

erfo

rma

nce

Presentation

20

Chapter 4

DISCUSSION

The results of the present study confirmed my hypothesis that older adults would

exhibit higher explicit memory performance when words were presented to conscious

awareness than when words were not presented within conscious awareness, but this

difference was much larger for words belonging to a theme or category than for words

not related to each other in any obvious way. Furthermore, the results supported my

prediction that words belonging to a theme or category would be more easily

remembered than words that were not related to each other in any obvious way, but this

was true only when words were presented within conscious awareness.

As I mentioned above, performance on the recall test was higher in supraliminal

conditions than in subliminal conditions. This result is consistent with research on the

facilitation of visual recall through the engagement of conscious processes (Aggleton &

Brown, 1999; Gardiner, 1988; Gardiner & Java, 1990; Gardiner & Java, 1991; Gardiner,

Java & Richardson-Klavehn, 1996; Jacoby, 1991; Rajaram, 1993; Tulving, 1985;

Wagner, Verfaeille, & Gabrieli, 1997; Yonelinas, 2002).

The deep processing phenomenon is evidenced in my study, which shows higher

explicit memory performance on the free recall exam in thematic conditions than in non-

thematic conditions. This finding resembled the results of Craik and Lockhart (1972),

showing the positive effect of deep processing on explicit memory.

21

Past research indicates that older adults are more likely to use semantic

associations than younger adults when performing serial recall tasks (Golomb, Peele,

Addis, Kahana, & Wingfield, 2008). Moreover, Englekamp and Wippich (1995) found

that, for older adults, word-relatedness enhances memory of subliminally presented

words. Conversely, younger adults remember more words that are not related to each

other in priming tasks than do older adults (Englekamp & Wippich, 1995). Younger

adults may not use categories to facilitate memory performance during the completion of

implicit memory tasks such as priming.

In contrast, older adults’ dependence on semantic content for memory

consolidation amplifies the effects of consciously perceived stimuli on explicit memory

test performance. By depicting the relationship between presentation and levels of

processing, my study demonstrated the importance of supraliminal effortful processes on

semantic facilitation of explicit memory. This claim is further supported by evidence

from Monti et al. (1996), who showed how meaning-based encoding processes through

the engagement of supraliminal memory processes enhance conceptually-driven aspects

of memory tasks. Additionally, Bradshaw and Anderson (1982) made advances in

conceptual priming and processing research by revealing the compound effect of

supraliminally-presented stimuli and thematic relatedness on category exemplar test

performance. Conclusively, the results from my study and previous research exemplified

the pivotal role that semantic associations play on conscious processes during explicit

memory tasks.

22

Notably, older adults falsely-remembered more words in the video presentation of

supraliminal stimuli than of subliminal stimuli. In other words, there were more false

alarms in the supraliminal than in the subliminal conditions. Supraliminality and the

application of cognitive effort seemed to have a stronger effect on incorrect guessing than

the effect of meaning-based memory processes, such as levels of processing, on memory.

Possibly, deep processing produces more accurate automatic memory trace formations in

older cohorts as a result of more efficient neural activation (Hinojosa, Martin-Loeches,

Munoz, Casado, & Pozo, 2004; Karni et al., 1995) whereas increased exertion of

resources help younger cohorts with situations that require the generation of novel ideas,

such as college or graduate school (Cabeza, Anderson, Houle, Mangels, & Nyberg,

1997).

Older adults who experience age-related memory declines due to the natural

degradation of interdependent cognitive systems could benefit from research findings on

how linguistic, semantic, and presentation tools might enhance memory (Luczsz &

Bryan, 1999). Researchers have relied on two principal theories to identify the sources of

aging phenomenon: Slowed central nervous system processing speed (Salthouse, 1980;

Salthouse, 1982; Salthouse, 1985; Salthouse, 1996) and diminished use of working

memory executive processes (Dempster, 1992; Parkin & Walter, 1992; Parkin, 1997;

Woodruff-Pak, 1997). By identifying the possible sources of age-related cognitive

declines, one can apply the findings from the present study to develop memory

preservation techniques for the aging mind, thus attempting to prevent the onset of the

debilitating disease of dementia.

23

Although the term “dementia” encompasses a variety of cognitive deficits, the

patient with dementia undergoes a series of phases before reaching the stage of clinical

diagnosis. Mild cognitive impairment diagnoses are given to individuals who experience

more serious cognitive decline than is expected for their age group or education level;

however, this class of impairment does not affect daily functioning (Gauthier et al.,

2006). The diagnoses of mild cognitive impairments and early onset of dementia-related

disorders tend to overlap (Santacruz & Swagerty, 2001). Preventative medicine could

provide memory-enhancing strategies to individuals with a genetic history of dementia.

The dual cognitive effects of meaningful, persistent stimuli could help reduce the risk of

the onset of dementia in that population.

Strengths and Limitations

The study’s design strengths bolstered its internal validity. For example, the recall

test was administered immediately after the study condition to reduce the time gap

between study and test. This measure increased the accuracy of word recall because

visual persistence of stimuli declines as the time gap increases between study and test

(Coltheart, 1980). Furthermore, by including two thematic word categories, I ensured that

the test measurement protocol was truly assessing the effect of relatedness on memory:

Using two thematic categories instead of one eliminated the possibility that recall could

be affected by category type instead of the intended independent variable, relatedness.

Equal variances among the two thematic word categories also protected the

internal validity of the study by ensuring that one category did not contain words of

higher relatedness than the other category. In other words, the equal variances among the

24

words within each thematic category buffered the study against possible biases of two

videos showing words from the same category with differing degrees of relatedness.

To accomplish the task of using two different categories, I used the partial

counterbalancing measure to present the four relatedness conditions in every possible

order, thus eliminating the possible confounding effect of a previous phase influencing

memory for words presented in a subsequent phase. However, the Latin-Square partial

counterbalancing measure did not eliminate all bias because the supraliminal condition

was always the first phase of each video. While a complete counterbalancing measure

would have removed this bias, it would have required that half of the videos present the

subliminal condition as the first phase, thus creating confusion for half of the participants

who saw the first set of words outside of their conscious awareness. In sum, I used a

partial counterbalancing measure to minimize this potential anxiety during the test phase.

Additionally, my decision to study individuals over 55 years of age was based on

aging literature revealing that 55 heralds a 16 year cognitive decline affecting list and text

recall in older adults. This cutoff is one of few widely accepted norms for investigating

age related decline in memory (Powell & Whitla, 1994). Using this age bracket to

conduct a longitudinal study, Zelinski and Burnight (1997) investigated normative

changes in memory and compared performance on intelligence tests of younger and older

adult cohorts. In their study, all age cohorts over 55 showed reliable decreases in

cognitive ability. Their findings confirm that normative age-related change in cognition

typically starts to appear at age 55, thus providing a solid age baseline for my study of

cognitive aging.

25

Furthermore, if I were to replicate this experiment, I would use the same time

limit methodology I used in the current study and not set a time limit for the testing

condition because older adults have slower processing speed than younger adults (Bryan

& Luszcz, 1996; Bryan & Luszcz, 2001). The rate of cognitive processes, such as

memory performance, varies widely from one participant to another and setting a time

limit would favor those with faster rates of cognitive processes. Thus, a time limit would

create a disadvantage for those with slower processing speeds.

In contrast to these strengths, various methodological limitations surfaced during

the development of my study’s experimental design. The small sample size of forty-eight

participants increased the risk of Type II error, which is the tendency to accept the null

hypothesis when it is false. My null hypothesis was that there was no difference in recall

between conditions. The small sample size may have underestimated the number of

significant memory score differences between the levels of the two independent

variables: relatedness and presentation. Although the heightened risk of committing a

Type II error was potentially problematic for my study, my hypotheses were still

supported by the results.

A small sample size also hindered my ability to draw generalizeable conclusions

about the entire senior population. Because I collected data from a convenience sample in

the community, the personalities and motivations of those who decided to volunteer for

my study could have differed from those who did not volunteer for my study. This

disparity could have biased my results to reflect positive attitudes toward academia or

community service. Furthermore, taking a convenience sample from a select group of

26

senior communities may not have adequately captured the true population mean with a

high degree of confidence. If I were to conduct this study again, I would allot more time

to participant recruitment in hopes of increasing my sample size to at least 100

participants.

My decision to draw a convenience sample instead of a random sample limited

the representativeness of my subject pool. Because I did not collect a random sample, the

economic, educational, and health characteristics unique to the senior communities

sampled may have biased the results in favor of individuals with high levels of self-

esteem and active lifestyles. Because I used a convenience sampling method for my data

collection, my distribution of mean scores may have deviated from the normal

distribution of population test scores. To adequately capture the complete constellation of

characteristics within my target senior population I should have used a random sample

because it would have fairly represented each characteristic without bias, effects of

outliers, and confounding covariates.

In addition, my method for recording false alarms exposed my study to

experimenter bias because it included a degree of subjectivity. I decided that an answer

was a false alarm if it shared structural similarity to the words in the video phases. The

subjectivity I used to determine whether the word was a false alarm may have positively

skewed the distribution of false alarm scores in my study. Furthermore, testing after each

phase would have been a better approach than testing after the video ended because

exposure to words from previous phases could have rendered ambiguous false alarm

assignments.

27

The sample also consisted of a disproportionate number of females compared to

males. Research shows that females in general have higher rates of depression than males

(Kessler et al., 1994; Regier et al., 1988; Robins et al., 1984). Royall, Palmer, Chiodo,

and Polk (2011) show that depression attenuates executive motor functions. Bo, Borza

and Seidler (2009) show that diminishing executive processes are related to cognitive

declines during aging. Therefore, depression could hasten the onset of dementia. Because

depression, a disease more prevalent in women than in men, is likely to produce

deleterious effects on aging memory, the disproportionate number of women in my

sample may have created negatively biased memory performance results.

Additionally, some participants experienced mild to moderate degrees of

frustration while watching the video, which escalated when they realized that a memory

test would immediately follow the video. My overreliance on the proctoring script and

the participants' uneasiness about taking a memory exam may have increased the

ambiguity in some of their responses and reduced the accuracy of scoring their answers.

Their anxiety may have hindered their ability to remember the exact structure of certain

words, producing a somewhat higher number of false alarms in supraliminal conditions.

Finally, to obtain a more accurate picture of the baseline cognitive functioning

status of the participant pool, I would use the Telephone Interview Questionnaire for

Cognitive Status, a cognitive assessment tool developed by Brandt, Spencer, and Folstein

(1988). An assessment of cognitive status could help me to screen individuals and

remove those who have stages of mild cognitive impairment or physical disabilities such

as blindness that would prevent them from participating in my study. Although my study

28

did not include individuals with these types of impairments, this screening tool would

ensure that I capture only individuals with high cognitive functioning.

Future Directions

Assisting cognitive aging through modern technology and educational media

creates a dynamic transmission of knowledge throughout younger and older generations.

To further analyze the relationship between relatedness and presentation, one might want

to incorporate elements from human-computer interface psychology literature to produce

websites that will facilitate the engagement of older adults. Websites designed with age-

relevant meaning-based contextual cues can assist older adults’ recall by activating

associative frameworks within their cognitive substrates. The results of such a study may

have important applications in the design of educational curricula in senior centers. For

example, teachers could use computers to present seniors with supraliminally-timed

reading exercises that consist of related material sparking consolidation of short-term

memories and association formations within cognitive networks.

My study of cognitive aging offers many benefits from a holistic health

perspective paving the way for further analysis of the interaction of many socio-

demographic variables that affect memory. Future studies analyzing the relationship

between age, cognitive functioning, risk for dementia, and test performance would create

a portrait of the dynamic relationship between these four variables and their significant

implications for gerontological health science research. These studies would chronicle the

progression of dementia and age-related cognitive impairments. Advances from this line

29

of research would not only impact science at an epidemiological level but also at an ionic

and cellular level.

The results from my study may assist those older adults with a genetic history of

Alzheimer’s disease because knowing how to facilitate recall could provide older adults

with a buffer against memory loss. My research findings that processing and timing of

presentation affect explicit memory in senior populations could mobilize future research

endeavors to study consciousness and its correlates with memory. Creative uses of deep

processing and semantic memory enhancing strategies could apply not only to senior

citizens but to other populations who would benefit from effortful retrieval and controlled

allocation of cognitive resources such as dyslexic or autistic children who might use

semantic networks for reading comprehension. Comparing healthy cognitive aging to

anomalous cognitive aging in later studies would impact neuropathological research

along the lines of preventative gerontological medicine and gerontological education.

Conclusion

Gerontology research throughout the past decade has chronicled the debilitating

effects of the gradual breakdown of cognitive systems in older adult populations. Despite

cognitive decline’s deleterious impact on memory capacity, compensatory memory

systems such as semantic associations and processing time can enhance memory

consolidation within complex neural networks. The activation of these networks unveils

the profound effect of meaning and consciousness on human experience and our reliance

on memory for survival.

30

Appendix

Final List of Forty Words Used in the Four Video Conditions

Video 1 Video 2

Them-Zoo Non-them (A) Non-them (B) Them-Veg Non-them (B) Them-Zoo Veg Non-them (A)

Phase I Phase II Phase III Phase IV Phase I Phase II Phase III Phase IV

Sup. Sub. Sup. Sub. Sup. Sub. Sup. Sub.

elephant grandchild unfasten cauliflower bandanna rhino onion test

hippo torchlight bandanna broccoli exhilarate tiger cucumber torchlight

leopard compactor incongruity lettuce unfasten panther pepper thumbprint

lion test rottweiler potato rottweiler chimp carrot notion

orangutan thumbprint skirt pea drive panda celery bankruptcy

crocodile notion buddy spinach skirt penguin corn middlebrow

gorilla middlebrow motorcycle peanut motorcycle kangaroo asparagus grandchild

giraffe groin exhilarate avocado baron snake garlic groin

bear technician drive pumpkin buddy zebra cactus technician

alligator bankruptcy baron squash incongruity gazelle beet compactor

Video 3 Video 4

Them-Veg Non-Them (A) Non-Them (B) Them-Zoo Non-Them (B) Them-Veg Them-Zoo Non-Them (A)

Phase I Phase II Phase III Phase IV Phase I Phase II Phase III Phase IV

Sup. Sub. Sup. Sub. Sup. Sub. Sup. Sub.

corn groin buddy chimp buddy cauliflower elephant notion

pepper notion exhilarate penguin incongruity broccoli leopard middlebrow

onion test motorcycle kangaroo bandanna spinach giraffe technician

asparagus technician unfasten snake skirt potato lion compactor

beet bankruptcy bandanna panther exhilarate lettuce crocodile torchlight

celery thumbprint skirt tiger unfasten avocado orangutan bankruptcy

cucumber torchlight rottweiler panda motorcycle pumpkin bear test

carrot grandchild drive rhino drive peanut alligator groin

garlic middlebrow baron zebra rottweiler squash gorilla thumbprint

cactus compactor incongruity gazelle baron pea hippo grandchild

31

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