One hot summer’s day a Fox was strolling through an orchard till he came to a bunch of Grapes just ripening on a vine which had been trained over a lofty branch. “Just the thing
to quench my thirst,” said the Fox. Drawing a few paces, he took a run and jump, but just missed the bunch. Turning round again with a One, Two, Three, he jumped up, but with no
greater success. Again and again he tried after the tempting morsel, but at last had to give it up. As the Fox walked away with his nose in the air, he said: “I am sure they are sour”.
It is easy to despise what you cannot get.
(The Fox and the Grapes, Aesop’s Fable)
Making decisions is like speaking prose – people do it all the time, knowingly or unknowingly.
(Kahneman & Tversky, 1984, p. 341)
Let us begin by breaking the overall topic of “The flexibility of olfactory preferences:
impact of decision-making processes” down into a sequence of smaller questions.
“The flexibility of olfactory preferences – are olfactory preferences really flexible?”
The extent to which olfactory pleasantness evaluation and preferences are flexible has been under debate in the literature. Some authors have argued that olfactory pleasantness evaluation and preferences are to some extent predetermined. This theoretical position, as well as empirical evidence to its support, has been criticized by authors insisting on the intrinsic ambiguity of olfactory perception and its sensitivity to modulation. An increasing amount of evidence seems to weigh in favor of flexibility. This thesis focuses on one of the factors that modulate preference changes: decision-making processes. The aim of this thesis is thus to describe to what extent olfactory preferences are sensitive to decision-making processes, and to investigate the underlying processes of such an influence.
“Impact of decision-making processes” – Do preferences shape choices, or do choices shape preferences, or both? (This discussion is not limited to olfactory preferences). According to the most dominant approach in contemporay social sciences, human beings indeed have a given set of preferences, and their choices – the decision-making processes that lead to a behavioral output – are a consequence of these preferences.
Preferences shape choices, and not the other way around.
An increasing amount of experimental evidence however suggests that rather than being stable, preferences are context dependent (e.g., Warren, McGraw, & Van Boven, 2011). According to this view, preferences do not reflect a set of values already present ex ante in an individual, but instead are a contextualized mental construction generated on a situational basis. If this is true, then preferences are the result of a multidimensional integration between numerous physical and cognitive dimensions. One of the most well established of these cognitive dimensions is precisely the impact of decision-making processes on current perceptual constructs.
Like the Fox in Aseop’s Fable, we devaluate options that we cannot get. More precisely, after a choice between equally liked stimuli, we evaluate the one we chose more positively, while devaluating the one we did not pick. These three steps (evaluation – choice – evaluation) constitute the free-choice paradigm (Brehm, 1956), a paradigm that has been used in hundreds of studies (for an overview, see e.g. Harmon-Jones & Mills, 1999).
If it is clear that decision-making processes can impact preferences, why study the impact of decision-making?
Despite the fact that there is now a substantial amount of work that demonstrates preference modulation following choice using this paradigm, little is known about the nature of the mechanisms underlying this effect. Most work assumes that cognitive dissonance reduction is the best way to theoretically interpret preference modulation following choice. Cognitive dissonance theory (Festinger, 1957) will be discussed in detail across this thesis, but in a nutshell, it claims that the choice puts the desirable aspects of the rejected option into conflict with the undesirable aspects of the chosen, which elicits discomfort (i.e., cognitive dissonance). Such discomfort can be reduced by ex-post realigning one’s preferences with the choice made – by devaluating the rejected option and valuating the chosen one more positively. This mechanism is thought to rely on explicit, conscious, mechanisms (Festinger, 1964).
There is, however, a surprising dearth of studies that directly examine whether the mechanisms at play are purely explicit, particularly since recent evidence suggests that implicit mechanisms may also be at play. Similarly, little is known regarding how long the preference modulation following choice lasts. Clarifying these two aspects would thus have important implications for cognitive dissonance theory, and more generally for the study of the acquisition and flexibility of preferences.
Why do we concentrate on the domain of olfaction?
Moreover, this thesis focuses on preferences in the olfactory domain. To the best of our knowledge, this work constitutes the first attempt to systematically study the impact of decision-making in this sensory modality. There are two important reasons which motivated our concentration on the domain of olfaction. First, we believe that the use of olfactory stimuli is ideally suited for studying implicit processes in preference modulation induced by choice because olfaction might rely more on implicit processes than vision or audition (Köster, 2005). Second, there is an ongoing discussion in the domain of olfaction about the flexibility of the evaluation of olfactory pleasantness. Our work contributes to this by investigating potential modulations caused by decision-making processes. We will discuss at length why we believe that studying this empirical question is important in the thesis objectives (section 2.5). All reported studies (apart from one) hence employed olfactory stimuli.
An overview of the structure of this thesis
This thesis is structured as follows: In chapter 2, we first define the concept of preferences, as used in this thesis, and discuss its assumed stability. We then review literature on the flexibility olfactory preference. Next, we present the main paradigms that have been used to investigate the way that decision-making influences preference flexibility driven. The main theoretical interpretation to such a modulation is discussed.
This theoretical part ends with the description of the three main thesis objectives. In summary, these are (i) investigating whether olfactory preferences can be modulated by decision-making processes; (ii) studying the level of processing (i.e., explicit vs. implicit) required for such a modulation to occur and (iii) testing the stability of this modulation.
In the empirical part (chapter 3), we present the nine different experiments we ran to fulfill these objectives. Eight of the nine reported experimental studies used variants of the free-choice paradigm, which was adapted to the goals of each particular study.
The first study investigates the modulation of olfactory preferences by explicit choices, and the extent to which such modulation could be present at an implicit level of processing (section 3.2). The second study investigates the extent to which blind choices can modulate olfactory preferences. In this study, participants were led to believe they were making certain choices, when actually they were predetermined by the experimenter.
We then tracked whether olfactory pleasantness changes, and whether this change depends on participants pre-existing pleasantness ratings or not (section 3.3). The third and fourth experiments address a methodological critique of the traditional free choice paradigm (Chen & Risen, 2010). The fifth and sixth studies investigate sniff patterns as a potential implicit behavioral correlate of preference modulation following choice (section 3.5). The seventh to ninth experiments explore the consolidation of implicitly shaped choice-induced preferences in long-term memory (section 3.6).
To conclude, we combine and integrate the theoretical and experimental parts of the thesis with a discussion of perspectives and limitations (chapter 4). We emphasize the importance of considering the role of implicit processing in olfactory preference flexibility and classical theories that explain postchoice preference modulation. We also develop future perspectives.