Choice-making, expectations, and positive affect
The study of choice-making has enjoyed considerable coverage in psychology over the past six decades. For instance, research has established that choosing can shape preferences (Ariely & Norton, 2008; Brehm, 1956; Harmon-Jones & Mills, 1999; Sharot, Velasquez, & Dolan, 2010), engender positivity (Sharot, De Martino, & Dolan, 2009), direct information processing (Hart et al., 2009; Jonas, Schulz-Hardt, Fischer, & Frey, 2006; Smith, Fabrigar, & Norris, 2008), and increase feelings of personal agency (Leotti, Iyengar, & Ochsner, 2010). Might choice-making also be an important determinant of whether people's experiences assimilate to expectations?
We suggest that the study of choice is logical in the context of expectation effects. Indeed, there are numerous domains in which people make choices between options with unknown but expected effects. For instance, decision makers choose between consumer products, investment opportunities, and medical treatments that vary in their anticipated outcomes. Importantly, the value of choice has become increasingly emphasized over the last several decades, notably in the health domain. For instance, there has been a steadily increasing shift toward patient involvement in healthcare decisions (i.e., “patient-centered medicine” or “shared decision-making”), as evidenced by the proliferation of web-based medical tools and decision aids, self-treatment alternatives, over-the-counter options, and direct-to-consumer medication advertising (Reyes-Ortiz, 1996; Stewart et al., 2003).
Recently, Geers and Rose (2011) provided a framework for understanding the role of treatment choice in the context of the placebo effect, a core example of an expectation assimilation effect (Olson et al., 1996). Placebo effects can be defined as physiological or psychological responses that can be directly attributed to expectations associated with a substance or procedure but not a result of the inherent power of that substance or procedure (Price et al., 2008; Stewart-Williams, 2004). Geers and Rose (2011) outlined several mechanisms to explain why choosing among placebo treatments might increase expectation assimilation effects, compared with conditions where expectations are provided without the availability of choice. Most notably for the current research, they proposed that choice-making should facilitate assimilative responses because of the activation of reward mechanisms in the brain and subsequently experienced positive affect in the context of the placebo treatment. Importantly, there are conceptual reasons that both choice-making and expectations should be connected with a positive affectivity mechanism. First, many placebo models suggest that treatment experiences assimilate to expectations because of the activation of dopaminergic mechanisms in the brain, which are associated with positive affect and reward processing (e.g., da Silva Alves et al., 2011; Diederich & Goetz, 2008; Lin, Wu, Chandra, & Tsay, 1981; Scott et al., 2007, 2008; for reviews, see Atlas, Wager, Dahl, & Smith, 2009; Benedetti, 2008). Interestingly, increasing dopamine also facilitates the construction of positive expectations for the future (Sharot, Shiner, Brown, Fan, & Dolan, 2009). Taken together, these two sets of findings suggest that there is a reciprocal relationship between reward mechanism activation in the brain and positive expectations. Second, the act of choosing has also been associated with increases in positive affect (Sharot et al., 2010; Sharot et al., 2009) and the activation of dopaminergic reward mechanisms (e.g., striatum; Sharot et al., 2009; Sharot et al., 2010; Tricomi, Delgado, & Fiez, 2004; for review, see Leotti et al., 2010).
In sum, both placebo expectations and choosing have been critically linked to positive affect via dopaminergic reward mechanisms. In typical placebo studies, participants are provided with positive expectations for a “treatment” but are not provided with a choice over the treatment. Although provided (i.e., non-chosen) placebo treatments have been shown to produce changes in dopaminergic activation and positive affect, we suggest that choosing among treatments with positive expectancies should produce even stronger expectation assimilation effects for two, interrelated reasons. First, positive affectivity experienced via choice-making and receiving a placebo expectation for a treatment may lead to more favorable evaluations of the treatment itself and the treatment context (although see the General Discussion section for a description of situations where this may not occur). Feeling more favorable about the treatment context should place people in the best position for their experiences to assimilate to the positive expectation. Second, the act of choosing is often seen as an expression of the self (Leotti et al., 2010), at least in Western, independent cultures (Iyengar & Lepper, 1999; Snibbe & Markus, 2005). If the self, which is viewed positively, becomes committed to a treatment via choice, then the selected option should become infused with positivity as well and facilitate the extent to which people will desire that the selected placebo treatment is effective (for related ideas, see Brehm, 1956; Harmon-Jones & Mills, 1999; Jonas et al., 2006; Sharot et al., 2010). Importantly, an influential placebo model (Price & Barrell, 1984; Price, Barrell, & Barrell, 1985; Price et al., 2008) suggests that the positive affect mechanism for expectation effects is strongest when desires for treatment efficacy co-occur with expectations. That is, placebo effects are strongest when expectations and desires for the treatment to work are both strong—and that the combination of strong desires and expectations operate through affect-based mechanisms. Thus, if choice-making engenders a greater desire for the treatment to be successful, this should amplify the placebo expectation effect via positivity experienced within and about the treatment context.
On the basis of a recent theoretical framework (Geers & Rose, 2011), it is suggested that choice over treatments should produce greater assimilative effects in the context of placebo expectations. Indeed, one recent study by Rose, Geers, Rasinski, and Fowler (2012) provided preliminary evidence in support of this hypothesis. Participants in experimental conditions were provided with two placebo treatments (i.e., inert hand lotions) that could ostensibly reduce pain from cold water. Some participants were given the opportunity to choose the “treatment” that they felt might work best for them, whereas other participants had the treatment selected for them by the experimenter. Participants permitted to choose among the treatments showed more assimilation to the placebo expectation (i.e., lower pain ratings) than did participants who had the treatment chosen for them. The Rose et al. study was the first to demonstrate that choice plays an important role in shaping placebo expectation effects.
Despite providing a useful preliminary investigation, there are several limitations to the Rose et al. study that necessitate follow-up research. First, the study was conducted in the domain of pain from cold water exposure. Although this finding is expected to have broad theoretical reach, it is nevertheless important to confirm that the results can be generalized to other domains, expectations, and experiences. Second, Rose et al. did not examine whether the impact of choice-making on expectation assimilation effects was mediated by changes in positive affect experienced in the treatment context. Third and finally, Rose et al. included only three conditions in their study: a condition where participants chose among two placebo treatments, a condition where participants had one of two placebo treatments selected for them by the experimenter, and a condition where participants did not have a choice or a placebo treatment. This design, with the absence of a choice/no expectation condition, opens up the possibility that simply having any choice—absent of expectations associated with the choice—might be sufficient to produce this pattern of results on its own. That is, given that making a choice can enhance perceived feelings of control, and given that control is related to reduced stress, discomfort, and pain (Maier, Laudenslager, & Ryan, 1985; Thompson, 1981), it is plausible that choice alone could reduce some discomfort (Rokke & Lall, 1992). Ruling out this alternative explanation is critical for theoretical and practical purposes.
In the current research, two experiments examined the role of choice-making in facilitating expectation assimilation effects using a novel paradigm. To first establish the usefulness of our paradigm, Experiment 1 was conducted as a replication of the three core conditions in the Rose et al. study. In Experiment 2, we investigated the mediating role of positivity regarding the treatment and included the full factorial design where we orthogonally manipulated expectations and choice-making.