Izuma and Muramaya (2013) have recently published an inspiring review article on the preference modulation induced by choice in the free-choice paradigm (Brehm, 1956). In this article, the authors have given an overview of the work that has been done since Chen and Risen (2010) have raised the concern that the results from this paradigm cannot unambiguously be interpreted as reflecting a true modulation of preference through choices.

Izuma and Muramaya (2013) have, besides others (e.g., Coppin, Delplanque, Cayeux, Porcherot, & Sander, 2010), referred to the present paper (Coppin, Delplanque, Porcherot, Cayeux, & Sander, 2012). They mentioned that its first two experiments are inconclusive regarding the true modulation of preference by choice, as they did not included a control for the issue raised by Chen and Risen (2010). We entirely agree, and are the first ones to point out this serious limitation (see our discussion of Experiment 2 page 8). Experiment 3, on the other hand, that controlled for the issue raised by Chen and Risen (2010), demonstrated a genuine modulation of preferences – about which Izuma and Muramaya agree with us.

However, we believe we need to clarify the conclusions one can draw from this series of three experiments. According to Izuma and Murayama (2013), we have erroneously claimed that the results from Experiment 1 and 2 are more than the mere artifact of the free-choice paradigm, based on results from Experiment 3 (Izuma and Muramaya, page 5, footnote 5). We would like to apologize if we improperly expressed ourselves – we had no intention of misleading the readers as to the degree of impact of our results. Because integrity is our first concern as scientists, we feel the need to more rigorously express our conclusions.

From the two first experiments, the modulation of pleasantness ratings observed can reflect a true modulation of preference by choice, a mere artifact of the free-choice paradigm, or both. There is no simple way to know, as no control was run at the time. These results cannot consequently unambiguously be interpreted as reflecting a modulation of preference by choice, and should therefore be considered with caution. Experiment 3, which used a different paradigm, does allow concluding that the experimental procedure has led to a genuine change in preferences. However, it does not enable a disambiguation of the results from experiments 1 and 2.
We hope that this comment may help the reader judge more accurately the proper impact of this series of experiments.


References
Brehm, J. W. (1956). Post-decision changes in desirability of choice alternatives. Journal of Abnormal and Social Psychology, 52, 384–389. doi:10.1037/h0041006

Coppin, G., Delplanque, S., Cayeux, I., Porcherot, C., & Sander, D. (2012). I’m no longer torn after choice: How explicit choices can implicitly modulate preferences for odors. Psychological Science, 21, 489-493. doi: 10.1177/0956797610364115

Coppin, G., Delplanque, S., Porcherot, C., Cayeux, I., & Sander, D. (2012). When flexibility is stable: Implicit long-term shaping of olfactory preferences. PLoS ONE 7(6): e37857.