Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Program Name/Specialization

Behavioural Neuroscience

Faculty/School

Faculty of Science

First Advisor

Rudy Eikelboom

Advisor Role

Professor of Psychology

Abstract

The Incentive Salience Theory (IST; Berridge and Robinson, 1998; 2016) has shown that wanting (craving) and liking (affective) processes can affect eating behaviour differently in animals. These processes often correlate but can dissociate (change differently) under certain circumstances as they rely on separate neural mechanisms (Berridge, 1996). More recently, work has been testing the IST in people by comparing broad food categories (Finlayson et al. 2007a; 2008). The results have been inconsistent, sparking debate about the theory's value for studying human feeding (Havermans, 2011; 2012).

This dissertation's aim was to explore if IST wanting and liking are independent processes controlling non-homeostatic feeding in humans. Secondly, does separating them have research value? Devising accurate methodology to assess wanting and liking in healthy undergraduate students was intertwined within these goals. Three online surveys explored how to measure these constructs. Study 1 (N=1508) found that participants reported that their most craved foods differed from their favourite tasting ones, suggesting a conceptual wanting and liking separation. Studies 2 (N=134) and 3 (N=219) found that chocolate and pizza cravings are quite specific and not well satisfied by other foods.

Three behavioural experiments used internal state manipulations to test for dissociations. The hypothesis was that the satiety and cue manipulations would cause wanting to vary greatly (decreasing after satiety or increasing after food cue exposure), while liking would remain stable. Experiments 1 (N=27) and 2 (N=46) used general satiety with potato chip, sensory-specific satiety (SSS) with chocolate consumption, or no change with water drinking. Participants rated wanting and liking for Hershey's kiss chocolate before and after. Both self-reported constructs decreased similarly after SSS, with minimal change after chip or water consumption. Experiment 3 (N=198) used satiety (general or SSS) or cue manipulations (imagining eating one's favourite chocolate or chips) in a 2x2x2 design. Hershey's kiss or Pringle's potato chip wanting and liking were rated before and after. Hershey's wanting and liking decreased similarly after SS satiety but did not change after the chocolate cue, despite an increase in hunger. For the Hershey’s kiss, potato chip manipulations produced opposite results to the chocolate manipulations. Pringle's wanting and liking showed only small reductions after the four manipulations (chocolate or chip satiety or cue). The chocolate and chip difference suggests that studies exploring the IST in humans should look at individual foods rather than generic categories.

The survey work showed a conceptual wanting-liking distinction. Despite the experimental work not finding any dissociation evidence, the IST may still be valuable in human feeding research. Future work needs more concise wanting and liking measures, including more acknowledgement of food specificity, e.g., by including a range of individually analyzed stimuli, to test the IST's generalizability to people.

Convocation Year

2021

Convocation Season

Fall

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