The Effect of Common and UniqueFeatures in Consumer Choice

RAVI DHARSTEVEN J. SHERMAN*

Consumer choice often involves a comparison among the available alternatives.Recent research finds that features shared by alternatives are canceled andgreater weight is placed on the unique features in choosing among the alternativesprovided. Building on this research, the authors propose that the attractivenessof the choice set can be enhanced or reduced by aitering which features appearunique. In the first study, this proposition is tested for choice probiems in whichsubjects choose or delay choice between pairs of alternatives that have eithershared bad features and unique good features (unique good pairs) or unique badfeatures and shared good features (unique bad pairs). As predicted, a greaterpercentage of subjects chose an alternative when there were unique good pairsthan when there were unique bad pairs. A second study allowed subjects toswitch from their initial choice to a new alternative with both unique good andunique bad features. The likelihood of switching to a new alternative was greaterfor subjects who made the initial choice from unique bad pairs. A third studyused the choice context to increase the attractiveness of a specific alternativeby making its good features appear unique. Finally, another study used think-aloud protocols to gain insights into the underlying mechanism.

When faced with a choice among several alterna-tives, an effective understanding of consumer be-

havior requires an analysis of whether choice occurs, aswell as the relative preference among various alternatives.Many formal analyses that examine forced choice assumethat features common to all the alternatives in the choiceset are canceled in the process of choice (Tversky 1972).Although the relative preference for an alternative shouldnot depend on whether its features are shared or uniquein the choice context, recent research suggests that theevaluation of an alternative can vary depending on thevalence of its unique features (Houston and Sherman1995). Given the importance of the unique features incomparative judgments, different choice contexts mayhighlight different features, and the valence of such fea-tures may influence the decision whether to choose aswell as the relative preference for a specific alternative.

We examine the effect on consumer preferences ofaltering the features that are seen as common or uniquein a choice set. Specifically, building on the notion ofdifferential focus on unique as opposed to common fea-tures, we explore the fact that the uniqueness of certain

*Ravi Dhar is assistant professor at the Yale School of Management,Yale University, New Haven, CT 06511, and Jim Sherman is professorin the Department of Psychology, Indiana University, tN 47405. Theauthors thank the editor, the associate editor, and the two reviewers fortheir useful comments and suggestions.

193

features in a given context can make the choice set appearmore or less attractive depending on whether the goodfeatures are unique and the bad features are shared or thebad features are unique and the good features are sharedin the alternatives. The effect on the overall evaluationsof the items in a choice set should affect the likelihoodof a person's making a choice as opposed to choosingneither and waiting to see other options. For example,consider a consumer who is debating between two vaca-tion options, both of which have good and bad features.We propose that the likelihood of not choosing either ofthe two spots is greater when the good features are sharedand the bad features are unique to the two vacation spotsthan when the good features are unique and the bad fea-tures are shared by the two options. This will be trueeven when the options in the unique bad choice set areobjectively as attractive as the options in the unique goodchoice set.

As the example suggests, we test our proposition byaltering the choice set under consideration such that eitherthe good or the bad features are unique and, thus, areseen as central and important. Further, we propose thatmanipulations of the uniqueness of the good or bad fea-tures can infiuence the willingness to switch to a newalternative. Specifically, after an initial choice betweentwo alternatives, subjects will be more likely to switchto a new alternative if the initial choice was betweenalternatives with unique bad and shared good features asopposed to shared bad and unique good features.

© 1996 by JOURNAL OF CONSUMER RESEARCH, Inc. • Vol. 23 • December 1996All righus reserved. 0093-530 l/97/23O3-0O03$02.0O

194 JOURNAL OF CONSUMER RESEARCH

Building on this notion, we show that the focus on theunique features can also alter the relative preference foran alternative when a new option is added to the choiceset. In particular, by virtue of the introduction of a newoption, an alternative whose good features appear uniqueand bad features appear common should gain in attrac-tiveness relative to other alternatives in the choice set.The predicted effects could have significant implicationsfor marketers' communication strategies in light of thepossibility that both choice shares and the likelihood ofchoosing at all can be affected by altering the shared andunique features of the alternatives in the choice set. Thus,the major goal of the present article is to extend ourunderstanding of feature distinctiveness on preference andto apply these results by outlining their implementationfor an analysis of choice incidence.

THE EFFECT OF THE FOCUSON UNIQUE FEATURES

Making comparisons is a fundamental psychologicalprocess, and many of our judgments of similarity andpreference involve comparing options in the set of alterna-tives that are available. Tversky (1977) proposed a modelfor the comparisoti process involved iti judgmetits of sitni-larity. This model is based on a feature-matching processin which similarity judgments are assumed to be the resultof the linear combination of the shared and distinctivefeatures of the objects being compared. It should be notedthat both shared and unique features are relevant for judg-ments of similarity even though the precise weights mayvary on the basis of task instruction. However, featuresthat are common to all the alternatives do not providediagnostic information for preference judgments, in con-trast to judgments of similarity, and are therefore notuseful in making a choice among alternatives. Regardlessof which item is chosen, the subject will end up withthe shared features. Accordingly, subjects may place lessemphasis on the common features and focus primarily onthe unique features of the paired items.

Although the greater emphasis on unique features maybe a reasonable heuristic when subjects must choose be-tween two alternatives (Meyer and Eagle 1982; Tversky1972), such a process may lead to systematic deviationsin choice incidence when subjects also have the optionof not choosing any of the alternatives or the option toswitch to a new alternative. In such cases, the absoluteor the overall value of an alternative should matter, andthis depends on both the shared and the unique featuresof the item. A decision process that leads to underempha-sizing some features will result in a distorted evaluation ofthe items in the choice set and, thus, a possible tendency tochoose or reject the same item depending on which of itsfeatures were emphasized.

Traditional research has focused on how consumerschoose among available alternatives in a forced-choicetask. More recent research has examined consumer deci-sion making when the option of not choosing any of the

alternatives is also provided (Dhar forthcoming; Huberand Pinnell 1994; Tversky and Shafir 1992). The evidencefrom this body of work indicates that subjects may decidenot to purchase if none of the alternatives appear attractiveor if subjects are uncertain about their most preferredalternative. If consumers focus mainly on unique featuresof the alternatives, there are two reasons why the decisionto not choose will be greater for a choice set consistingof unique bad pairs than for a choice set made up ofunique good pairs.

One reason for the difference in the preference for notchoosing occurs because the attractiveness of the samealternative will vary with the context. Consider an alterna-tive that is presented as a part of a unique good pair suchthat the two objects have unique good features but sharetheir bad features. As indicated by the feature-matchingmodel (Houston, Sherman, and Baker 1989), the shared(bad) features will be underweighted in the choice pro-cess. In addition, the unique (good) features of the twoalternatives will receive greater attention. Thus, the alter-native is likely to appear attractive. However, the compar-ison process should produce a different outcome whenthe very same alternative appears as part of a unique badpair such that both alternatives share good features andpossess unique bad features. In this case, it is the uniquebad features that carry greater weight in the choice pro-cess. The differential prominence of the good and badfeatures in the two contexts should result in making thealternative either more or less attractive.

A second reason that choice incidence may differ oc-curs because of the potential difference in decision diffi-culty in the two contexts. Recent research suggests thatmaking trade-offs between competing alternatives canarouse confiict, resulting in a tendency to postpone choice(Tversky and Shafir 1992). Note that if the paired itemsshare bad features, but each possesses unique good fea-tures, the decision is framed as a trade-off between goodfeatures. In contrast, the same comparison process isframed as a trade-off between bad features when paireditems share good features and possess unique bad fea-tures. The choice situations that require trade-off amongnegative features may be potentially more difficult thanthose that require trade-off amotig positive features. Ac-cordingly, the unique bad choice context may be morelikely than the unique good context to result in a prefer-ence for not choosing. On the basis of this reasoning, wepropose the first hypothesis.

HI : The preference for a no-choice option is greaterwhen subjects are choosing between pairs ofcomparable alternatives that have unique badand shared good features than when they choosebetween pairs that have unique good and sharedbad features.

STUDY 1Method

Procedure. The subjects were 290 students at a north-eastern university, and they were each paid $2.00 for their

EFFECT OF COMMON AND UNIQUE PRODUCT FEATURES 195

participation. The task involved making decisions in sev-eral different choice problems. The cover story stated thatthe researcher was interested in understanding consumerbehavior. Subjects were asked to imagine that they werethinking of making decisions in the categories described.The task instructions emphasized that there were no rightanswers and that subjects should choose the option thatbest refiected their response to the situation described. Sub-jects were told that, as in real choice situations, they alsohad the option of not choosing either of the alternativesprovided. A choice set was then presented, and the subjectshad to choose between selecting one of the two options orlooking for new alternatives.

The study design was such that the same object waspaired with an alternative to create a unique good pair inone case and a unique bad pair in another case. Thisrequired a minimum of four choice-set combinations dif-fering in terms of the composition of the choice set. Intwo of the four choice sets, subjects saw two alternativeswith the same good features and different bad features.In the remaining two choice sets, the two alternatives hadcommon bad features and unique good features. Eachsubject made decisions in four different choice problems:two containing descriptions of unique bad pairs and twocontaining unique good pairs. The two alternatives in eachcondition were presented side by side, and the commonand unique features were alternated. Subjects were ran-domly assigned to the four conditions (with 70-75 sub-jects in each), and the order in which the different prob-lems were reviewed was also randomly determined.

Stimulus Material. Four different problems were usedto test the hypothesis. The categories used were objects(apartments, vacation spots) and persons (blind dates,same-sex work partners). Two sets of unique good andbad features were used to construct the stimuli; Gl andG2 are used to denote the set of good features, and B1and B2 are used to denote the set of bad features. Descrip-tive feature lists for the person and objects were similarto those used by Houston and Sherman (1995) and hadbeen proved to be relatively equally attractive to the stu-dent subjects. Each alternative shared its good but not itsbad features with one other description, while sharing itsbad but not its good features with another alternative. Bypairing each alternative with one other alternative withwhich it shared some features, four pairs of alternativeswere constructed for each choice problem: two uniquegood pairs and two unique bad pairs. An example of achoice set for the vacation problem is provided in Appen-dix A.

Results and Discussion

Hypothesis 1 predicted that the preference for a no-choice option would be greater for unique bad pairs. Theresults are presented in Table 1 and are discussed herefor the vacation problem. Consistent with the hypothesis,the percentage of subjects who preferred to look for other

v a c a t i o n s p o t s i n c r e a s e d b y 1 4 p e r c e n t { z = \ . l , p < . 1 0 ) .One explanation for the difference in the no-choice sharecould be that the features of the pair G1-B2 are not asattractive as those of G2-B1. Thus, a replication was donefor a second choice pair such that the alternative thatpreviously created the unique good pair now created theunique bad pair and vice versa. If alternative G2-B1 wereseen as more attractive than G1-B2, there is a greaterlikelihood to not choose the alternative in the third columnover that in the fourth column. However, the percentageof subjects that selected the no-choice option increasedby 29 percent (z = 3.5, p < .01) when subjects saw G2-Bl instead of G1-B2. Further, the percentage of subjectswho chose the same alternative (Gl-Bl or G2-B2) waslower when it was a part of unique bad pair. As seen inTable 1, similar results were obtained for the other threecategories. The mean share of the no-choice option in-creased by 17 percent {z = 5.8, p < .01) when the choicewas between unique bad pairs.

An overall test of the hypothesis was conducted acrossthe four categories using a binary logit model. The depen-dent variable was a 0-1 dummy variable, where 1 denotesthat subjects did not choose either of the two alternatives.The independent variables were as follows: (1) a dummyvariable UNQGOOD, which had a value of 1 if the uniquefeatures were good, and (2) two-way interactions betweenthe feature manipulation and the four product categories.Consistent with the hypothesis, the coefficient for UNQ-GOOD was highly statistically significant (x^(l) = 22.4,p < .001). The coefficients for the interaction betweenunique features and category-specific dummies were non-significant (p's > .2), indicating that the effect of featuremanipulation was similar across product categories.

Study 1 demonstrated that the nature of overlappingfeatures can have a systematic effect on the preferencefor not choosing from the choice set. Specifically, subjectstended to look for a new alternative when the choicecontext highlighted the bad features. Note that the individ-ual alternatives of each choice set were similar in attrac-tiveness. As stated previously, the greater tendency notto choose from the unique bad pair could be attributed toan aversion to making trade-offs between negative fea-tures or to the perceived lower attractiveness of the twoalternatives in that choice context. One way of discrimi-nating between the two alternative explanations would beto look at the willingness to switch to a new alternativeafter making a choice from a unique good pair or froma unique bad pair.

Study 2 allowed subjects to switch to a new alternativewith both unique good and unique bad features after aforced choice between unique good or unique bad pairs..Although the status quo bias suggests that there is a gen-eral tendency to stay with the initial choice, it does notpredict a difference between subjects who made an initialchoice between unique good pairs and those who chosebetween unique bad pairs. If the greater preference forthe no-choice option when presented with the unique badpairs in study 1 was due simply to greater difficulty in

196 JOURNAL OF CONSUMER RESEARCH

TABLE 1

EFFECT OF COMMON AND UNIOUE FEATURES ON THE DECISION TO DEFER CHOICE

Problem 1: vacation spot:Choose AChoose SNo choice

Problem 2: apartment:Choose AChoose 6No choice

Problem 3: blind date:Choose AChoose SNo choice

Problem 4: work partner of the same sex:Choose AChoose 8No choice

n (290 total)

Pair

A, G1-B1e, G2-B1

283240

282250

302842

15246070

1

A, G1-B1e, G1-B2

222454"̂

162460

222058+

10187273

Pair

A, G2-B2e, G1-B2

363826

283141

262945

32343472

2

A, G2-B2e, G2-B1

252055"

232156*

101575"

22205 2 "75

* For the difference in the no-choice share reiative to the adjacent pair, p = .10." For the difference in the no-choice share relative to the adjacent pair, p = .01.

making trade-offs between negative features, then no spe-cific prediction is made about the decision to switch to anew alternative when presented with unique bad pairs asopposed to unique good pairs.

In contrast, if the differences in not choosing refiecteda difference in evaluation of the alternatives because ofthe focus on unique features, there should be a systematicdifference in the postchoice response. If the initial choiceis among alternatives comprising unique good pairs, sub-jects are relatively satisfied with their choice because thechosen options' bad features are underweighted (Houston^Sherman, and Baker 1991). If the new alternative hasunique good and unique bad features, there is no compel-ling reason for switching, which results in a tendency tostay with the initial choice. However, if the initial choiceis between unique bad pairs, subjects will be relativelydissatisfied with their choice because its bad aspects areprominent. On the basis of this discussion, we proposeour second hypothesis.

H2: After an initial choice, the preference forswitching to a new alternative with both uniquegood and unique bad features is greater whenthe initial choice involves unique bad pairs thanwhen the initial choice involves unique goodpairs.

STUDY 2

MethodProcedure. The subjects were 290 students at a north-

eastern university, and they were paid $2.00 for their

participation. The task and the instructions were the sameas those in study 1. After the initial choice, subjects weretold that a new alternative was now available and wereasked to state whether they would like to stay with theirchosen option or switch to the new alternative.

The same design as in study 1 was used, with twounique good and two unique bad choice sets. In all condi-tions, the third alternative was identical and had bothunique good and unique bad features in relation to thetwo initial alternatives. Each subject made two decisionsfor the four choice problems: two problems containingdescriptions of unique bad pairs and two problems con-taining unique good pairs. The first decision involvedchoosing from the unique good or the unique bad pair.The second decision involved deciding between switchingto the new alternative or staying with the status quo.Subjects were randomly assigned to the four conditions(with 70-75 subjects in each). The order in which thedifferent problems wei"e reviewed was also random.

Results and Discussion

Hypothesis 2 predicted that the preference for switch-ing to a new alternative would be greater when the initialchoice was between unique bad pairs. The results arepresented in Table 2 and are discussed here for the vaca-tion problem. In general, there was a preference to remainwith the initial choice, as predicted by the status quo effect(Samuelson and Zeckhauser 1988). Moreover, consistentwith the hypothesis, the mean percentage of subjects whopreferred to switch vacation spots was 17 percent higher

EFFECT OF COMMON AND UNIOUE PRODUCT FEATURES 197

TABLE 2

EFFECT OF CHOOSING FROM PAIRS WITH COMMON AND UNIOUE FEATURESON THE DECISION TO SWITCH TO A NEW ALTERNATIVE

Problem 1: vacation spot:Choose AChoose SOption to switch:

Stay with choiceSwitch to C

Problem 2: apartment:Choose AChoose SOption to switch:

Stay with choiceSwitch to C

Problem 3: blind date:Choose AChoose eOption to switch:

Stay with choiceSwitch to C

Problem 4: work partner of the same sex:Choose AChoose 6Option to switch:

Stay with choiceSwitch to C

Pairi

A, G1-B1 A,B, G2-B1 e.

5248

8712

5842

7624

4456

8020

3862

7624

G1-B1G1-B2

4555

683 2 "

4456

6238*

5842

6634*

5248

5248"

Pair 2

A, G2-B2 A,B. G1-B2 e.

5446

8020

4456

7228

5644

8614

4654

7624

G2-B2G2-B1

5050

6634*

5842

5644*

3565

683 2 "

5050

6238*

NOTE.—W = 290.* For the difference in the switching share reiative to the adjacent pair, p = .10." For the difference in the switching share reiative to the adjacent pair, p = .01.

(z = 1.9, /? < .10) when presented with the two uniquebad pairs rather than the two unique good pairs. As seenin Table 2, similar results were obtained for the otherthree categories. The mean switching share to the newalternative across all choice problems for the unique goodpairs was 20 percent; it increased to 37 percent when theinitial choice was between unique bad pairs (z = 5.9,p < .01).

An overall test of the second hypothesis was conductedacross the four categories using the same binary logitmodel as in study 1. Consistent with the hypothesis, thecoefficient for UNQGOOD was highly statistically sig-nificant (x^(l) = 20.7, p < .001). The coefficients for theinteraction between unique features and category-specificdummies were nonsignificant (p's > .2), indicating thatthe effect of feature manipulation was similar across prod-uct categories.

The results of study 2 are consistent with the notion thatsubjects focus on the unique features of the alternatives inthe choice set. Such a focus leads to a more negativeevaluation of items from a unique bad choice set andthus a greater willingness to switch to a new alternative.Further, these results cannot be accounted for by the po-tential difference in the trade-off difficulty in the two

contexts. An alternative explanation for the results mayarise when subjects' prior beliefs about the set of potentialalternatives are weak relative to the contextual informa-tion. In such cases, subjects who saw the unique goodpairs may have formed different expectations than sub-jects who saw the unique bad pairs. Eor instance, subjectswho saw the unique bad pairs observed variance in nega-tive attributes and may thus expect to see more negativealternatives in relation to subjects who saw unique goodpairs and variance in positive features. Although the dif-ferent expectations could potentially explain the differ-ence in no-choice option reported in the first study, itwould not explain why subjects who saw unique bad pairswere also more likely to switch to the new alternative.

If subjects indeed focus more on unique than on com-mon features during the choice process, such differencesshould be revealed by think-aloud protocols during deci-sion making. This prediction can be tested by countingthe number of thoughts expressed about each alternativeas they relate to the common or unique features. In addi-tion, previous research suggests that subjects are morelikely to pay attention to negative features (Pratto andJohn 1991). Finally, we can compare subjects who dochoose between the two alternatives with those who do

198 JOURNAL OF CONSUMER RESEARCH

not choose and prefer to consider a new alternative. Con-sider subjects faced with unique bad pairs. Among thesesubjects, those who refuse to choose should mention morethoughts about the unique features than those who dochoose one of the two items. On the other hand, for uniquegood pairs, mentioning more thoughts about the uniquefeatures should be associated with a greater tendency tochoose. On the basis of this discussion, we formulatedour third hypothesis.

H3: Subjects are more likely to mention the uniquefeatures of the alternatives in the choice set thanthe shared features. In addition, nonchoosersare more likely than choosers to mention theunique features when choosing from unique badpairs. Choosers are more likely than nonchoos-ers to mention the unique features when choos-ing from unique good pairs.

STUDY 3

Method

Procedure. The subjects were 40 undergraduate stu-dents at a northeastern university, and they were each paid$5.00 for their participation. Each subject first receiveddetailed instructions about the task and the importance ofthinking aloud while responding to the problems. Beforestarting the actual task, subjects were given one problemto practice thinking aloud while being recorded. As inthe previous studies, the unique good and unique badpairs were balanced across choice problems and subjects.

The task included the four problems used in studies 1and 2. Because the decision process underlying the resultsof the two studies was expected to be similar, only thescenario from study 1 was used. The protocols were ana-lyzed by two judges, including one of the authors, whocounted the number of features expressed about the twoalternatives by the subjects for each choice problem ineach choice context. Next, these thoughts were linkedwith unique or common features of the two alternatives.A thought such as ' 'Both have good party spots'' countedas a favorable thought for both alternatives. The in-terjudge reliability was 94 percent, and disagreementswere resolved by discussion. To test the effect of contexton differential focus, we compared the number of com-mon and unique features mentioned in the process ofdeciding from the choice sets with unique good andunique bad pairs. We also examined the number of uniqueand common features mentioned for the choosers andnonchoosers for the unique good and unique bad pairsseparately.

Results and Discussion

The effect of the choice-set manipulation on the prefer-ence for a no-choice option replicated the results of theprevious studies. There was a statistically significant in-crease in the no-choice share for the unique bad pairs

(14 percent in the automobile problem, 16 percent in thevacation problem, 20 percent in the blind-date problem,and 14 percent in the work-partner problem).

Table 3 reports the mean number of thoughts for theunique and common features for the two choice contexts.In the four choice problems, the number of thoughts aboutthe unique features was significantly greater than the num-ber of thoughts about the common features (3.4 vs. 1.1,z = 5.7, p < .01). This finding is consistent with thepremise that subjects focus their attention on the uniquefeatures. Moreover, negative features were more likelyto be mentioned than positive features, both when suchfeatures were unique (3.9 vs. 2.8, z = 2.9, p < .01) andwhen they were common (1.5 vs. 0.8, z = 1.7, p < .10).

We also examined the differences between choosersand nonchoosers in each choice context. When the choiceset consisted of unique good pairs, subjects selecting theno-choice option mentioned fewer unique features (2.4vs. 3.2, z = 1.9, /? < .01) than subjects who made achoice. In contrast, subjects who preferred not to choosefrom unique bad pairs mentionecl more unique features(4.4 vs. 3.2, z = 3.1, p < .01) than subjects who didmake a choice. Thus, subjects who acted most in accor-dance with the underweighting of common features weremost likely to exhibit the predicted choice behavior. This isfurther highlighted in the ratio of unique to common featuresthat were stated by the choosers and nonchoosers in the twochoice contexts as shown in the note to Table 3.

STUDY 4

Choice and Preference for Uniqueness

As stated earlier, the feature comparison process forchoosing differs from a process in which the two alterna-tives are separately evaluated and then these evaluationsare compared. The notion of shared and unique featureshas meaning only in the context of a direct comparisonof the choice alternatives. The previous studies used thechoice context to highlight either the good or the badfeatures of the alternatives in the choice set. The focusled to an increase (for unique good pairs) or a decrease(for unique bad pairs) in the attractiveness of the choiceset as a whole. Not only can the choice context affect theattractiveness of the choice set as a whole; it can alsoaffect the attractiveness of any single alternative in thatset. To the extent that the context highlights the goodfeatures of a particular alternative (and downplays its badfeatures), there should be an increase in its relative attrac-tiveness for the reasons described previously.

Consider the choice between two vacation spots, bothof which have different good and different bad features.Now a third alternative is added, an alternative whosegood features are the same as the good features of oneof the other two alternatives in the choice set. This createsa perception of relative uniqueness for the alternative withdifferent good features, which in itself may increase itsrelative attractiveness. In addition, the alternative that

EFFECT OF COMMON AND UNIQUE PRODUCT FEATURES 199

TABLE 3

EFFECT OF UNIOUE GOOD AND UNIOUE BAD CONTEXT IVIANIPUU^TION ON THE MEANNUMBER OF THOUGHTS FOR GOOD AND BAD FEATURES

Common featuresUnique features

Total

Choice

.93.2

4.1

Unique good pairs

No choice

2.12.4

4.5

Total

1.52.8

4.3

Choice

1.03.2

4.2

Unique bad pairs

No choice

.74.4

5.1

Total

.83.9

4.7

NOTE.—Data are presented as tnean nutnber of thoughts. For the unique good pairs, the ratio of unique to commonfeatures stated were as foilows: for choosers, 3.5; for nonchoosers, 1.2; ail artifacts, 1.8. For the unique bad pairs,the ratio of unique to connmon features stated were as foiiows: for choosers, 3.2; for nonchoosers, 6.2; ail artifacts,4.9. For the unique good pairs, 54 percent of subjects tnade a choice, and 46 percent made no choice. For theunique bad pairs, 38 percent made a choice, and 62 percent made no choice (difference between conditions, p =.01).

shares its bad features with the new alternative makesthem less salient. On the basis of this discussion, wepropose the following hypothesis.

H4: The relative preference for an alternative canbe increased by introducing a new alternativethat makes its good features appear unique andits bad features appear common.

Method

Procedure. The subjects were 220 students at a north-eastern university, and they were each paid $2.00 for theirparticipation. The task and instructions were the same asin previous studies. A between-subjects design was used,with the three conditions differing in the composition ofthe choice set. In the control condition, subjects saw achoice set in which the two alternatives had differentgood and different bad features (Gl-Bl and G2-B2). Ina second condition, a third alternative, C (G2-B1), whichhad the same good features as the second alternative andthe same bad features as the first alternative, was addedto the choice set. This made the good features of the firstalternative and the bad features of the second relativelyunique. Thus, the first alternative should gain in attrac-tiveness. In the third condition, the new alternative, C"(G1-B2), highlighted the good features of the second al-ternative and downplayed its bad features and highlightedthe bad features and downplayed the good features of thefirst alternative. This should lead to an increase in theattractiveness of the second alternative. Each subjectmade decisions for four choice problems in one of thethree treatment conditions. Subjects were randomly as-signed to the three conditions, and the order of the prob-lems was randomly determined.

Stimulus Material. The choice problems were thesame as in previous studies. Two sets of unique good andbad features were used to construct the control choice set.A combination of these features was used to construct

the third alternative in the two treatment conditions. Inorder to maximize the effect of feature distinctiveness,the new alternative had the effect of making the goodfeatures more unique as well as making the bad featuresmore common. An example of the stimulus materials forthe vacation problem that highlights the unique good fea-tures of the first alternative and the unique bad featuresof the second alternative is shown in Appendix B.

Results

Hypothesis 4 predicted that the relative preference foran alternative will be greater when it is perceived to haveunique good features among the set of alternatives underconsideration. Suppose that C' shares good features withB and bad features with A, and C shares good featureswith A and bad features with B. The focus on uniquefeatures predicts that the addition of C to the set [A,B}will increase the attractiveness of A relative to B. Thesame reasoning leads to the prediction that the additionof C" to the set [A,B} will increase the attractiveness ofB relative to A. Let P(A,- B) be the proportion of consumerswho chose A from the choice set [A,B), and let P(A;B,C')and P(A;6,C") be the proportions of consumers whochose A from the set {A,B,C'} and {A,B,C"}, respec-tively.

Using the measure developed by Simonson and Tver-sky (1992), Pc'(A,fi) measures the popularity of A relativeto B, inferred from the choice set {A,B,C'). The prefer-ence for uniqueness implies that Pc'(A,fi) > Pc'(A;fi).We predict that the relative preference for the alternativewhose good features are' perceived as unique will increasein that triple in relation to the other triple as well as thepairwise coniparison. The results are presented in Table4 and are illustrated in the text for the vacation problem.The percentage of subjects who preferred A over B (i.e.,Pc'(A;B)) in the triple [A,B,C'] was 58 percent (42 per-cent for A vs. 30 percent for B) in comparison with 42percent in the pair {A,B}. Also as predicted, the relative

200 JOURNAL OF CONSUMER RESEARCH

TABLE 4

EFFECT OF COMMON AND UNIQUE FEATURES ON THE DECISION TO PREFER THE UNIOUE ALTERNATIVE

Problem 1: vacation spot:Choose AChoose 6Choose C or C"

Problem 2: apartment:Choose AChoose 6Choose C

Problem 3: blind date:Choose AChoose SChoose C o rC"

Problem 4: work partner of the same sex:Choose AChoose SChoose C or C"

n (220 total)

A, G1-B1B, G2-B2

4258

6238

3862

5644

73

A's good uniqueA, G1-B1B, G2-B2C, G2-B1

423028

582220

364222

46322274

B's good uniqueA, G1-B1B, G2-B2C", G1-B2

2 4 "4832

44*3220

2 1 "5524

35*461973

* For the difference in reiative preference for A between the triples, p = .10." For the difference in reiative preference for A between the triples, p = .01.

preference for A over B in the triple [A,B,C"} decreasedto 33 percent in the triple that made B's good features lookmore unique. The difference in the relative preference ofA over B between the two triples was 25 percent (z = 3.1,p < .01). Across the four problems, the relative preferencefor A over B increased by 10 percent when A's goodfeatures appeared unique and decreased by 8 percentwhen B's good features appeared more unique. The differ-ence between Pc'(A,-fi) and Pc (A;B) was 18 percent (z= 5.9, p < .01). Thus, the data support the notion thatthe attractiveness of an alternative can be enhanced if thechoice context makes its good features appear relativelyunique and its bad features appear common in comparisonwith those of other alternatives in the choice set.

GENERAL DISCUSSION

The current set of studies achieves several goals. Previ-ous research has shown that a focus on the features thatare unique to the alternatives has effects on the amountof time it takes to choose (Houston et al. 1991) and onthe overall satisfaction with the choice and the evaluationsof the chosen and rejected alternatives (Houston and Sher-man 1995). Our research adds to these effects in severalways. Study 1 showed that the preference for not choosingany of the available alternatives was greater for uniquebad than for unique good paits. Study 2 extended thisfinding to subjects' greater willingness to switch to a newalternative after an initial choice from unique bad ratherthan unique good pairs. These results extend the effect

of feature distinctiveness to the emerging domain of con-textual infiuence on choice incidence. Study 4 also sup-ported the effect by showing that the addition of a thirdalternative can alter the relative preference for the othertwo alternatives in ways thait are predictable from thesalience of unique features.

An important implication of these outcomes is that theevaluation of the choice set and of the individual itemsin the choice set will vary depending on the context pro-vided by the items in the choice set. Thus, the very sameitem can be evaluated quite differently depending on theother items that are present in the choice set. The ideathat the evaluation or judgment of an item can vary as afunction of the background context is not recent. Contexteffects in judgment and choice have been a focus of studyfor many years (e.g., Helson 1964; Simonson and Tversky1992). An underlying theme of these findings is that thepreference for a particular alternative can be enhanced ordiminished depending on whether the nature of trade-offcontrast is favorable or unfavorable to that option. Thesecontext effects are posited to occur because of the greatdifferences in value along the relevant dimension of thedifferent stimulus sets.

The process involved, based on the focus on unique fea-tures, is quite different from other processes that have beenused to account for the effects of adding new altematives.Although the judgment of a target stimulus is different de-pending on the set of altematives in which this stimulus isembedded, the different choice sets do not differ in value.The same item (e.g., an apartment) is evaluated differently

EFFECT OF COMMON AND UNIOUE PRODUCT FEATURES 201

in the context of two different but equally attractive apart-ments. In other words, the different contexts do not differalong the evaluative dimension. Rather, the comparison pro-cess that is engaged in by the decision maker leads to anunderweighting of some features of the altematives and aheightened salience of other features. Thus, context effectscan be brought about not only by the perspective providedby the set of relevant items but also by the set of relevantfeatures that are considered.

Not only do the present studies demonstrate such con-text effects, but additional evidence for the focus processwas provided in study 3. Think-aloud protocols demon-strated that subjects focused their attention on the uniquefeatures of the available altematives. In addition, the de-gree to which subjects chose an available option as op-posed to seeking to look further was predictable from thefeatures that were focused on, as indicated by the think-aloud protocols. This evidence regarding the processesunderlying differences in preferences and satisfaction isan important step.

Study 4 shows that the addition of a new, third alterna-tive can affect the relative preference of the two otheralternatives. Much work in the judgment and decision-making literature has been devoted to an understandingof how new entries into a market will affect the marketshare of other alternatives. A number of different contexteffects in consumer choice, such as the attraction and thecompromise effects, have been identified in the literature(Huber, Payne, and Puto 1982; Simonson and Tversky1992). The process involved, based on the focus onunique features, is quite different from other processesthat have been used to account for the effects of addingnew altematives. The effects in study 4 depended onwhich of the features of the altematives were renderedunique or shared by the addition of a new option. Onceagain, these results indicate that it is not the objectivevalues of the altematives taken independently that con-tribute to preference; rather, it is the comparison processengaged by the preference task that brings about theseeffects. The same item can be chosen and valued highly,chosen and valued very little, rejected and valued highly,or rejected and valued very little depending on the fea-tures of the other altematives in the choice set.

Marketing Consequences

Our findings suggest that marketers can affect con-sumer preferences by manipulating the choice set of com-peting alternatives. Because few products achieve com-plete dominance in the marketplace, the choice of productcomparisons also implicitly determines the nature of thetrade-offs that consumers are asked to make in order tochoose. In particular, when designing comparative ads,marketers could encourage consumers to consider the dif-ferent advantages of their product in relation to those ofcompetitors rather than the disadvantages of competitors'products in relation to their product. For instance, adver-tising wars that provide reasons for not buying competi-

tors' products may prove counterproductive and resultin consumers' not purchasing at all. This would furtherreinforce findings that negative comparative advertisingmay be inferior to positive comparative advertising interms of claim acceptance (Jain 1993) by showing itseffect on choice. In a similar vein, the effect that negativecampaigning may have on voter turnout would be aninteresting topic for future research.

The finding that an option that has relatively uniquegood features tends to appear more attractive and to havea higher choice probability provides another reason toconstruct the context carefully when comparative adver-tising is used. Specifically, the present results suggesthow the context can be used to create perceived unique-ness and favorable associations for a specific alternative.Consider the case in which a prospective student has todecide among different types of educational institutions.We suggest that if a small liberal arts college comparesitself to Ivy League institutions that have similar benefits(i.e., faculty reputation, breadth of courses, student diver-sity), it should make itself relatively more attractive byhighlighting the unique benefits of the smaller college.More generally, marketers should take this effect intoconsideration when presenting various comparable alter-natives. Just as previous research has shown that differen-tiation based on a unique, but irrelevant, attribute canincrease the attractiveness of the differentiated brand(Carpenter, Glazer, and Nakamoto 1994), our results sug-gest that perceptions of uniqueness can be created by thedecision context.

Future Research Directions

Most of the work to date with regard to the feature-matching model of choice has focused on whether thepresence of unique good or bad features and the enhance-ment of the distinctiveness of good or bad features affectthe choice made from a set of alternatives and the levelof satisfaction with that choice. This work can be charac-terized as primarily answering " i s " questions (Zanna andFazio 1982). Is there an effect of the manipulation? Isthere a phenomenon to be explained? Research indeeddemonstrates that the presence and salience of uniquefeatures have interesting and significant effects on choice.

Now that these first-generation " is" questions have beenasked and answered, it is time to move on to the nextgeneration of questions: "when" and "how" questions.With regard to "when" questions, it will be important toinvestigate the limiting conditions of the effects and thepreconditions under which these effects obtain. For example,given that the focus on unique features is basically a heuristicapproach to making choices (in that not all of the featuresof all the candidates are considered), the effect is likely tobe weaker when the common features are important or self-relevant. In that case, one might want to give full and carefulconsideration to all known attributes. Similarly, the effectof common features may be moderated by the importance ofthe unique features of the altematives. In this vein, Chemev

202 JOURNAL OF CONSUMER RESEARCH

(1995) reports that when one of the unique features is per-ceived to have primary importance, common features en-hance the polarization of consumer preferences, leading toa divergence of relative choice shares.

In addition, the effect may hold only when there are afew altematives. With larger numbers of alternatives, theidentification of common and unique features is unwieldy,and an approach such as elimination by aspects might beadopted until the choice set is small enough to allowfeature matching. Similarly, the effect may also weakenwhen there is an increase in the number of common fea-tures relative to the unique features. Finally, an issue thatis pertinent to all context effects in choice is whetherthese effects weaken when subjects are asked to makerepeated choices.

With regard to ' 'how'' questions, we must advance ourunderstanding of the psychological processes underlyingthe observed effects. There have been few studies inwhich indicators of process have been collected. Excep-tions are the response-time results reported by Houstonet al. (1991) and the think-aloud protocol data reportedin our study 3. Other kinds of processing data would beimportant for answering "how" questions. For example,the use of Mouselab decision software to examine dataconceming information that subjects actively seek out inthese choice situations could be extremely useful.

In sum, the present set of studies accomplishes severalgoals. First, implications of feature distinctiveness havebeen extended to an analysis of choice incidence, and thethink-aloud protocols serve as a beginning for data thatprovide empirical support for the process outlined. Theeffect was shown to support predictions conceming thedecision to forgo making a choice, the willingness toswitch to a new altemative after an initial choice, and theeffect of adding a third alternative on the preferencesfor the two other altematives. Finally, implications formodeling consumer choice and for the effects of product-feature evolution in markets have been specified. Futureresearch will test and expand on these implications.

APPENDIX A

Example of Unique Bad, Shared Good Altematives

Example of Unique Good, Shared Bad Alternatives

Place ABeautiful sceneryPollution problemPlenty of nightspotsExpensiveGood museumsLong travel time

Place BBeautiful sceneryOvercrowdedPlenty of nightspotsPossible bad weatherGood museumsPoor transportation

Place ABeautiful sceneryPollution problemGood museumsExpensivePlenty of nightspotsLong travel time

Place BGood restaurantsPollution problemGood theatersExpensiveAttractive beachesLong travel time

APPENDIX B

Vacation SpotsImagine that you are planning for a vacation. You have

obtained information on three vacation spots with thefollowing attributes. Which one would you prefer?

Example of Making K's Good Features Uniqueand Bad Features Common

Spot AGood restaurantsAttractive beachesGood theatersPollution problemExpensiveLong travel time

SpotsPlenty of good

nightspotsBeautiful sceneryGood museumsOvercrowdedPoor transportationPossible bad

weather

Spot CPlenty of good

nightspotsBeautiful sceneryGood museumsPollution problemExpensiveLong travel time

In the situation described above, I would: (circle one)A. Choose spot A B. Choose spot B C. Choose spot C

Example of Making B 's Good Features Uniqueand Bad Features Common

Spot AGood restaurantsAttractive beachesGood theatersPollution problemExpensiveLong travel time

SpotsPlenty of good

nightspotsBeautiful sceneryGood museumsOvercrowdedPoor transporta-

tionPossible bad

weather

Spot C"Good restaurantsAttractive beachesGood theatersOvercrowdedPoor transportationPossible bad weather

In the situation described above, I would: (circle one):A. Choose spot A B. Choose spot B C. Choose spot C

[Received August 1995. Revised May 1996. BrianSternthal served as editor and Robert J. Meyer

served as associate editor for this article.]

EFFECT OF COMMON AND UNIQUE PRODUCT FEATURES 203

REFERENCES

Carpenter, Gregory S., Rashi Glazer, and Kent Nakamoto(1994), "Meaningful Brands from Meaningless Differenti-ation: The Dependence on Irrelevant Attributes," Journalof Marketing Research, 31 (August), 339-350.

Chemev, Alex (1995), "The Effect of Common Features onBrand Choice: Moderating Effect of Attribute Impor-tance," working paper, Fuqua School of Business, DukeUniversity, Durham, NC 27708.

Dhar, Ravi (forthcoming), "Consumer Preference for a No-Choice Option," Journal of Consumer Research.

Helson, Harry (1964), Adaptation-Level Theory: An Experimen-tal and Systematic Approach to Behavior, New York:Harper & Row.

Houston, David A. and Steven J. Sherman (1995), "Cancella-tion and Focus: The Role of Shared and Unique Features.in the Choice Process," Journal of Experimental SocialPsychology, 31 (July), 357-378.

, Steven J. Sherman, and Sara M. Baker (1989), "TheInfluence of Unique Features and Direction of Comparisonon Preferences," Journal of Experimental Social Psychol-ogy, 25 (March), 121-141.

-, Steven J. Sherman, and Sara M. Baker (1991), "Fea-ture Matching,' Unique Features, and the Dynamics of theChoice Process: Predecision Conflict and Postdecision Sat-isfaction," Journal of Experimental Social Psychology, 27(September), 411-430.

Huber, Joel, John W. Payne, and Christopher Puto (1982),"Adding Asymmetrically Dominated Altematives: Viola-tions of Regularity and the Similarity Hypothesis," Journalof Consumer Research, 9 (June), 90-98.

and Jon Pinnell (1994), "The Impact of Set Qualityand Decision Difficulty on the Decision to Defer Pur-chase," working paper. Duke University, Durham, NC27708.

Jain, Shaliendra P. (1993), "Positive versus Negative ComparativeAdvertising," Marketing Letters, 4 (October), 302-320.

Meyer, Robert J. and Thomac C. Eagle (1982), "Context-In-duced Parameter Instability in a Disaggregate-StochasticModel of Store Choice," Journal of Marketing Research,19 (February), 62-71 .

Pratto, Felicia and Oliver John (1991), "Automatic Vigilance:The Attention-Grabbing Power of Negative Social Infor-mation," Journal of Personality and Social Psychology,61 (September), 380-391.

Samuelson, William and Richard Zeckhauser (1988), "StatusQuo Bias in Decision Making," Journal of Risk and Un-certainty, 1 (March), 7-59.

Simonson, Itamar and Amos Tversky (1992), "Choice in Con-text: Trade-off Contrast and Extremeness Aversion," Jour-nal of Marketing Research, 29 (August), 281-296.

Tversky, Amos (1972), "Elimination by Aspects: A Theory ofChoice," Psychological Review, 79 (July), 281-299.

(1977), "Features of Similarity," Psychological Re-view, 84 (July), 327-352.

and Eldar Shafir (1992), "Choice under Conflict: TheDynamics of Deferred Decision," Psychological Science,3 (November), 358-361.

Zanna, Mark P. and Russell H. Fazio (1982), "The Attitude-Behavior Relation: Moving toward a Third Generationof Research," in Consistency in Social Behavior, Vol.2, ed. Mark P. Zanna, E. Tory Higgins, and C. PeterHerman, Ontario Symposium, Hillsdale, NJ: Eribaum,283-301.