Experiment 2 - Blind choices but not random preferences: Does the impact of blind

congruency with pre-existing preferences?

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Abstract

Using the free-choice paradigm (Brehm, 1956), it has been shown that pleasantness ratings are changed after choice. This change has been interpreted as an evidence of choice shaping preferences. However, Chen and Risen (2010) have recently argued that the free-choice paradigm suffers from a methodological flaw: choice may simply reveal preexisting preferences. They demonstrate mathematically that changes in measured pleasantness that are consistent with choice do not mean that any genuine choice-induced preference modulation has occurred. To demonstrate a true impact of choice on preferences, some studies have used a “blind-choice” design, where choice is experimentally manipulated, and cannot consequently reveal preexisting preferences. However, such a design mixes two types of choices: choices congruent with a participant’s initial ratings (which we assume to reflect pre-exiting preferences) and choices incongruent with them. Based on Chen and Risen’s assumptions, one would expect the modulation of postchoice pleasantness ratings in congruent, but not in incongruent choices. To the contrary, if choice does impact preferences, one would expect the modulation of postchoice pleasantness ratings to occur in both congruent and incongruent choices. Here we tested these two alternative hypotheses directly, by dissociating congruent choices from incongruent choices in a blind-choice design. In our data, pleasantness ratings were not significantly changed after choice – neither for congruent, nor for incongruent choices. Hence, the data did not permit us to tease apart congruent and incongruent choices.

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3.3.1. Introduction

According to the most dominant approach in contemporary social sciences, the choices we make are the result of our preferences. This does not however mean that the link between choices and preferences is uni-directional: a large body of empirical work shows that choices, rather than just reflecting preferences, can in turn shape them (for reviews, see notably Ariely

& Norton, 2008; Harmon-Jones & Mills, 1999).

One frequently used paradigm in this context is the “free-choice paradigm” (Brehm, 1956). This paradigm includes 3 stages: (i) a first pleasantness rating of individually presented stimuli, (ii) binary choices between stimuli, which were initially rated as similarly pleasant (i.e., difficult choices) or as differently pleasant (i.e., easy choices), (iii) a second pleasantness rating of all stimuli similar to the first pleasantness rating. After difficult choices, participants typically rated the chosen option as more pleasant and the rejected option as less pleasant than during the first set of ratings. This classical empirical finding has been replicated many times, and interpreted as evidence for a modulation of preferences by choices.

However, the methodological validity of the free-choice paradigm to investigate choice-induced preference change has lately been seriously questioned (see Chen, 2008; Chen

& Risen, 2010; Risen & Chen, 2010). To be concise, the central point raised by Chen and Risen (2010) is the following one: using the free-choice paradigm, choice could merely reveal preexisting preferences. If the initial ratings were subject to some random noise, one would then expect the second set of ratings (in stage iii) to be, on average, more consistent with the choices – hence biasing towards up-evaluations of chosen and down-evaluations of rejected items. This implies that one may observe postchoice pleasantness rating change, in the absence of any underlying preference change (see Chen and Risen, 2010; Coppin, Delplanque, Porcherot, Cayeux, & Sander, in press, for a more detailed account). Since then, several new studies have aimed at clarifying the extent to which the effects observed in previous work that uses the free-choice paradigm are robust to this critique (Coppin, Delplanque, Bernard, Cayeux & Sander, in revision; Coppin et al., in press; Egan et al., 2010;

Izuma et al., 2010; Sagarin & Skowronski, 2009a, 2009b; Sharot, Velasquez, & Dolan, 2010).

So far, two main empirical approaches have been adopted to demonstrate an influence of choice on preferences while circumventing Chen and Risen’s point. The first approach has

been to compare the hedonic modulation in the classical rating-choice-rating (RCR) sequence with a control condition that modifies the sequence of measurements—a rating-rating-choice (RRC) condition—in which choice can reveal preferences ex post, but not influence the second rating (Chen & Risen, 2010; Coppin et al., in revision, section 3.4 of this work; Izuma et al., 2010). The second approach has been to use a “blind” choice procedure, that is, a giving participants the feeling they are making a choice although actually the outcome of the choices were pre-determined by the experimenter (Egan et al., 2010; Sharot et al., 2010).

We will focus here on the second approach, i.e. the use of a “blind” choice (for a discussion of the first approach, see Coppin et al., in revision). Note that the “blind-choice”

strategy has been recognized by Risen and Chen (2010) as a valid approach to address the methodological issue under scrutiny even if “it is not clear that dissonance theory or self-perception theory would necessarily predict attitude change following a blind choice” (Risen

& Chen, 2010, p.18). In such a design, choice cannot be logically conceived as revealing anything about preference, as « chosen » and « rejected » objects are manipulated, thus establishing the effect in circumstances to which Chen and Risen’s argument does not apply.

The fact that post-“choice” pleasantness modulation has been observed even in this setting (Egan et al., 2010; Sharot et al., 2010) has been taken as evidence that effects of choice on preferences are more than mere artifacts of the free choice paradigm.

However, we believe that such a blind-choice design mixes two types of choices:

choices that one can call congruent vs. choices incongruent. Our rationale is this: even in difficult choices, the ratings between the two pairs of stimuli are often slightly different.

Based on this small difference, it would be possible to predict the choice that a participant is likely to make (assuming the noise in preference measurement via pleasantness ratings is not too drastic). In a blind-choice design, this means that while some of the manipulated choices are choices that participants would have been likely to make freely, some others are not. In other words, the “chosen” and “rejected” options can be in accordance with pre-existing preferences (in the first rating session, A was rated 5, B was rated 5.2; in the blind choice session, B is “chosen” over A). Such choices can consequently be considered as congruent choices regarding a participant’s initial ratings. To the contrary, the “chosen” and “rejected”

options may also be inconsistent with the initial ratings (in the first rating session, A was rated 5, B was rated 5.2; in the blind choice session, A is “chosen” over B). Such choices would be incongruent choices regarding a participant’s initial ratings. The extent to which the match

between this manipulated choice and initial ratings matters in post-choice preference modulation matters is currently unknown.

This distinction seems, however, important to consider. In assuming that pleasantness ratings, as well as choices, reflect, at least partially, stable underlying preferences (assumptions from Chen & Risen, 2010), one would predict postchoice pleasantness ratings modulation in congruent choices but no modulation in incongruent choices. To the contrary, assuming that choice does impact preferences, one would predict postchoice pleasantness ratings modulation to occur in both congruent and incongruent choices. Previous studies which pioneered the blind-choice design (Egan et al., 2010; Sharot et al., 2010) did not aim at investigating this question. They consequently did not distinguish between congruent and incongruent choices, or report the respective number of each. Further work is therefore needed to support the interpretation that preferences really impacted choices. The experiment presented here aims at testing these two alternative hypotheses by systematically separating congruent and incongruent choices. Based on Chen and Risen’s assumptions, one would hypothesize the modulation of postchoice pleasantness ratings in congruent, but not in incongruent choices. To the contrary, if choice does impact preferences, one would expect the modulation of postchoice pleasantness ratings to occur in both congruent and incongruent choices.

3.3.2. Methods

Participants

Sixty-five participants (57 females, mean age = 25.28 years ± 9.88 years) participated in the experiment after completing a consent form. All participants reported a normal sense of smell.

They were individually tested and were asked not to wear any fragrance during the days of testing. They were paid 10 Swiss francs for their participation.

Stimuli

Sixteen odors were used in this experiment. Their mean ratings are provided in Table 1. We showed in previous studies (Coppin, Delplanque, Cayeux, Porcherot, & Sander, 2010; Coppin et al., in revision) that these odors’ pleasantness ratings can be modulated after choice in the free-choice paradigm.

Procedure

First, participants were asked to rate the pleasantness, familiarity and intensity of sixteen (target) odors on continuous scales presented on a computer screen. Participants had to move a vertical marker with the mouse across a horizontal line and click to indicate their rating. Participants judged the pleasantness from “very unpleasant” (left on the scale = 1) to

“very pleasant” (right on the scale = 10), the subjective familiarity from “not familiar at all”

(left) to “very familiar” (right) and the subjective intensity of the odor from “not perceived”

(left) to “very strong” (right).

Second, participants were asked to make choices between two empty pens, presented to them as containing very weak concentrations of smell. Participants were told that the experiment aims at examining unconscious decision-making mechanisms. Thus, they were instructed that they would not be able to consciously perceive these smells but that they could be still able to choose one inside of a given pair. Once they made a choice inside the pair of empty pens, they were told which smell they had “chosen” and which smell they had

“rejected”, using the pens containing regular concentration of smell. Eight pairs were created for this choice phase on the basis of these first pleasantness ratings: (a) four difficult pairs of odors – smells within these pairs had been rated as similarly pleasant (i.e., difficult choice conditions for one half of the trials; mean rating differences = 0.08 ± 0.39 on the 10-point subjective scale) and (b) four easy pairs of odors – smells within these pairs had been rated differently in terms of pleasantness (i.e., easy choice conditions for one half of the trials;

mean rating differences = 3.68 ± 1.54 on the 10-point subjective scale). For half of the difficult pairs, if smell A was rated as more pleasant than smell B, A was presented as

“chosen” leading to a congruent “choice”; in the other half of the difficult pairs, if the smell A was rated as more pleasant than smell B, A was as “rejected”, leading to an incongruent

“choice”. For the four easy pairs, the odor presented as chosen was always the one with the more positive pleasantness rating of the pair (only “congruent” choices) to ensure that participants believed in the cover story. Each smell appeared in only one pair.

Third, after the choice session, participants were again requested to assess the pleasantness, familiarity and intensity of the sixteen odors (see Table 2). Finally, participants were debriefed and dismissed.

During the entire experiment, the order in which odors or pairs of odors were presented was controlled. For each presentation of the odor, participants were instructed to smell the odor during two inspirations at most.

Odor Mean pleasantness before

choice

Mean pleasantness after choice

Standard soap fragrance 6.08 (± 2.17) 5.96 (± 2.43)

Sandalwood 4.28 (± 2.13) 4.22 (± 2.05)

Shampoo fragrance 7.69 (± 1.80) 7.76 (± 1.71)

Fig flower 5.50 (± 2.01) 5.08 (± 2.34)

Lilac flower 6.50 (± 2.03) 6.73 (± 1.90)

Lavender flower 6.17 (± 2.33) 6.27 (± 2.45)

Violet flower 5.61 (± 1.84) 5.05 (± 1.95)

Yoghurt 2.30 (± 1.82) 2.39 (± 1.91)

Aladinate (floral note) 3.56 (± 1.88) 3.54 (± 2.10)

Raspberry flower 5.46 (± 1.68) 5.40 (± 1.43)

Melon 3.50 (± 1.93) 3.27 (± 1.94)

Tutti-frutti 6.86 (± 2.55) 6.86 (± 2.51)

Pineapple 7.75 (± 1.88) 7.07 (± 1.89)

Magnolia 6.14 (± 2.04) 6.14 (± 1.81)

Beer 3.12 (± 2.16) 2 92 (± 2.16)

Leather 3.20 (± 2.19) 2.88 (± 2.14)

Table 2: Name of the 16 odors used in Experiment 2 and their mean ratings. Standard deviations are presented in parentheses.

Data analyses

We removed from the analyses all pairs in which both smells received an identical rating from the participants, as we could not classify choices within these pairs as congruent or incongruent (approximately 11.9% of the difficult pairs). Preference-change induced by choice is typically reported when choices are difficult, i.e. when the difference between the pleasantness ratings of the two paired odors obtained before the choices is small. In this manuscript, we present only the results obtained in the difficult condition.

3.3.3. Results

First, we performed a repeated measures analysis of variance (ANOVA) with our three factors of interest as within-subject factors in the difficult pairs: the factors Choice (blindly chosen, blindly rejected), Congruency (congruent choices, incongruent choices) and Time (before choice, after choice) on the pleasantness scores. This analysis revealed a significant main effect of Time, F(1,63) = 6.42, p = .014, η2 = .09, showing that pleasantness ratings were decrease over time (see Figure 4), and a significant interaction between the factors Choice and Congruency, F(1,63) = 7.46, p = .008, η2 = .11 showing that the effect of the choice on the difference in pleasantness scores differed according to whether the choice was congruent or incongruent. The other interactions and main effects were not significant.

Second, we conducted a repeated ANOVA with the factors Choice (Chosen, Rejected) and Congruency (Congruent choices, Incongruent choices) in the difficult pairs on the difference between prechoice and postchoice ratings, which is the typical dependent measure of interest in the free-choice paradigm. This analysis revealed neither a main effect of the factor choice or congruency, Fs (1,63) = .79, .68, ps = .377, .411, respectively, nor an interaction between these factors, F(1,63) = 1.26, p = .266 (see Figure 4). In the absence of any significant effect in this analysis, we could not further test whether congruent and incongruent choices showed a different pattern of pleasantness ratings modulation following choice.

Figure 4. Mean difference in pleasantness scores in the difficult-choice condition as a function of whether the odor was presented as chosen or rejected and whether this choice was congruent or incongruent with pre-existing preferences. Difference was calculated as the postchoice score minus the prochoice score. Error bars represent standard errors of the mean.

3.3.4. Discussion

The aim of this experiment was to tease apart in a blind-choice design (Egan et al., 2010;

Sharot et al., 2010) congruent choices, i.e. blind choices consistent with a participant’s existing ratings, versus incongruent choices, i.e. blind choices inconsistent with the pre-existing ratings. We argued that this separation is theoretically relevant: if choice does impact preferences, one would predict postchoice pleasantness ratings modulation to occur in both congruent and incongruent choices. In contrast, if choice merely reflects preferences, but does not itself influence later preferences, one would predict postchoice pleasantness ratings modulation only for congruent choices. Separating congruent and incongruent choices would consequently enable a direct test of choice impact on preferences.

In this experiment, we observed no significant modulation in either condition. As illustrated by Figure 4, pleasantness ratings decreased after in comparison to before choice for both chosen and rejected odors in both congruent and incongruent choices.

We can of course only speculate about the reason(s) why we failed to observe an impact of blind choices on preferences using our variant of the blind-choice paradigm. We

can hypothesize that it is due to a failure of the cover story. However, judging by their surprise in the debriefing or their frustration regarding the impossibility to smell the “very weak concentration pens” or their bragging while they felt like they could detect something, participants seem to truly believe in the cover story. Another possibility is that the failure of observing an impact of blind choices on preferences is due to the few number of trials. It is possible - each of our 65 participants only got 2 congruents trials and 2 incongruents trials. So far, all studies showing pleasantness ratings modulation following choice in the olfactory modality have been conducted while participants were actually smelling the odors (Coppin et al., 2010; Coppin et al., in press, Coppin et al., in revision). Such designs rely on experienced utility, i.e. the subjective pleasure experienced with a given object, and not on predicted utility, which refers to the beliefs about the subjective pleasure experience with an object (Kahneman et al., 1997). However, using a blind-choice paradigm, Egan et al. (2010) demonstrated postchoice preference modulation using gustatory stimuli. Their design has however been severly criticized by Risen and Chen (2010). Another possibility is that the failure of observing an impact of blind choices on preferences is due to too much noise in the measurements. Error is inherent to any measurement. Here, error has two sources. First, there is some noise error while measuring pleasantness ratings (and assuming they are a reflect of pre-existing preferences). Second, we assumed that, in the case of congruent choices, the presented choices were those which participants would have made and in the case of incongruent choices, choices that participants would have not made. However, this assumption is wrong in, on average, 25% of the cases (e.g., Chen & Risen, 2010).

To conclude, in this blind-choice design, we could not demonstrate an impact of blind choices on preferences. In the next section of this thesis, we will explore the second main empirical approach has been adopted to demonstrate an influence of choice on preferences, consisting in comparing the hedonic modulation in the classical rating-choice-rating (RCR) sequence with a control condition that modifies the sequence of measurements—a rating-rating-choice (RRC) condition—in which choice can reveal preferences but not influence the second rating.