As an interim summary, we have shown (Exp 1) that blind choices can affect subsequent preferences, and that this effect is abolished in the computer-choice (instructed) condition. However, we acknowledge one potential difference between Experiment I and II that tempers this overall conclusion. Our caveat relates to a possibility that symbol strings are common substitutions for vulgarities. Thus, seeing the nonsense scribbles (e.g., “%^!x *&()%) in Experiment I may have emphasized the alternatives and the decision that followed. These symbols were not present in Experiment II. Thus, we run an additional group of participants on a second computer choice task (Exp III) that incorporate nonsense scribbles as in Experiment I.
Data from 20 participants (males = 8, females = 12; age range = 18-35) were included in the analysis. Data from three additional participants were eliminated due to excessive number of trials with no response (> 25%).
The procedure was identical to Experiment I except that participants were informed that the computer will make a choice for them and that after observing the choice they should indicate by pressing the left or right button the option the computer had choose for them.
No choice-induced changes in preferences were observed (). As in Experiment II, ratings did not shift after the decision making stage for either selected (P > 0.3) or rejected (P > 0.8) stimuli. Neither were changes in ratings for selected and rejected stimuli different from each other (P > 0.6).
To formally test for the effects of choice, agency and emphasis (due to nonsense scribbles) on rating change in all participants, we conducted a linear regression analysis entering the shift in ratings (post-choice – pre-choice) for selected and rejected options as the dependent measures. The independent measures included choice, agency, and emphasis (which were entered each as 1 or 0), and the interaction between choice and agency, and choice and emphasis (which were entered as the product of the two variables). Results of a step-wise regression revealed that the model which best explained the change in ratings was one that included only the interaction between choice and agency (Beta = 2.3), F (1,119) = 6.7 P < 0.01. This suggests that shifts in preference are guided by choice where participants believe they are instrumental in the decision making process, but not when a computer instructs the choice.
Our results demonstrate that choices not only reveal preferences alone but also shape them. We show that even when decisions are made randomly, and are not guided by pre-existing preferences, these choices change expectations of hedonic outcome. Furthermore, choice-induced change in preference is observed only when participants believe they have been instrumental in making a decision, and not when the decision was instructed by a computer.
The behavioral finding that making a decision can change our overall preferences is consistent with recent fMRI data. We have previously shown that a signal in the caudate nucleus, that tracks expected hedonic outcome, was altered by choice and resulting in enhanced post-choice activity for selected, and reduced post-choice activity for rejected, items (Sharot De Martino & Dolan, 2009
). It is important to note that we do not rule out the likelihood that choices can be guided by pre-existing preferences. On the contrary, we have previously shown that decisions between two equally rated options are predicted by a neurophysiological signal in the caudate nucleus that indexes the expected hedonic impact of the option, consistent with the idea that decisions do indeed mirror a neural representation of pre-existing preferences (Sharot De Martino & Dolan, 2009
). These prior results, coupled with the current findings, point to a conclusion that choices reflect and shape hedonic expectancies.
The claim that choice shape preferences is also consistent with a previous study demonstrating preferences changes in a context where non-human primates and children make blind choices, but not where an experimenter makes the choice for them (Egan, Santos & Bloom, 2010
). The current results extend those findings to adults (using different dependent variables, stimuli, and operationalization of the blind choice), suggesting that preference re-evaluation following a blind choice is not constrained to agents lacking a fully developed brain, language, and/or mature cognitive capacities.
More broadly, the current findings can be interpreted within the framework of both cognitive dissonance theory and self perception theory. According to cognitive dissonance theory, observing one’s (blind) decision can trigger dissonance between the initial cognition that the two options are equally preferred and an action which commits to one option over another (Festinger, 1957
). This psychological tension is reduced by re-evaluating the alternatives post-choice, such that the options are no longer perceived as equal. When a computer, rather than an agent, makes the selection dissonance does not arise, due to absence of agency in committing to an action which conflicts with an initial cognitive evaluation. We note that the choices made here were hypothetical, and it is possible that different results may be observed for decisions that involve real consequences.
Within self perception theory (Bem, 1967
), it is assumed that subjects infer their preferences by observing their choices. The theory’s explanation for the present results would be as follows: participants believed they were learning their preferences, and updated their explicit ratings accordingly. However, when a computer made the decision, preferences were not updated as those choices were not perceived as reflecting the participants’ preferences.
In sum, the results support Brehm’s (1956)
initial claims of choice-induced changes in preference in a study that steers clear of the methodological flaw associated with the “free choice paradigm”. Post-choice re-evaluation may serve an adaptive purpose by promoting commitment to our selected action, thus preventing us from wasting time dwelling on what may have been, and/or getting stuck by constantly changing our minds. Interestingly, enhanced commitment to our chosen options likely occurs when decisions are random, such as blindly sticking a pin in a map to choose a travel destination, or flipping a coin to make a life altering decision.