Categorical Perception and Levels of Processing in the Psychology of Eating
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University of Surrey Taste; Beyond sensation, the role of papillae, categorical perception and levels of processing in the psychology of eating Luke Jefferies A thesis submitted for the award of the degree of Doctor of Philosophy Department of Psychology Presented: 2009 UNIVERSITY OF SURREY ProQuest Number: U510354 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest U510354 Published by ProQuest LLO (2019). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLO. ProQuest LLO. 789 East Eisenhower Parkway P.Q. Box 1346 Ann Arbor, Ml 48106- 1346 Acknowledgements Firstly I would like to acknowledge the considerable support and encouragement of Prof. R. Shepherd who was able to guide me throughout the project. Your support was most helpful and critical, especially with my distance from the university during writing up. Your willingness to read through drafts was a considerable assist! I would also like to thank Prof. I.R.L. Davies for his scholarly knowledge of Categorical Perception and cognitive psychology which proved essential to the project. I would also like to acknowledge the support of Prof. J. A. Groeger for his guidance on Levels of Processing. I would especially like to thank Prof. R. Shepherd & Prof. I.R.L. Davies for their invaluable support with statistics. I would like to thank my supervisors for developing and nurturing my skills and abilities as a psychologist through the highs and lows of the project. I would like to recognise their passion for their subjects that have developed my own interests in the psychology of eating and CP (and other issues of cognitive psychology). I hope this PhD forms the first steps towards my own direct and original contribution to professional psychology. I also appreciated the input and viewpoints of my examiners who highlighted the strengths and weaknesses of my work. Additionally I would like to thank the BBSRC and Unilever for their funding. I would also like to thank Unilever and Dr R. Hurling for providing me an experience of how research into the psychology of eating is used in industry. I would like to thank my family for their support throughout my studies, especially my mam (Zena), dad (Kevin), stepdad (Ant) and last but not least my stepmam Chris. Further I would wish to acknowledge Ant, for nurturing the virtue of going the extra mile and working extra hard to gain one’s goals. I thank my parents for providing the solid foundation from which I have grown. I would not have been able to have completed this PhD without all your support. I also thank my sisters Jodie and Kayleigh. I also would like to thank all my grandparents. This PhD is dedicated to my new little baby niece, Breanna. Abstract Our understanding of the psychology of food choice and eating has gaps when it comes to the understanding at the basic cognitive level. This thesis aimed to address this gap, applying theories and methods not previously used with the sense of taste. This would include investigating taste perception and taste buds. Additionally the nature of tastant categories and the mnemophysics of flavour will also be investigated. Research has shown that papillae numbers affect perception ability; i.e., whether someone is a non-taster, taster or super-taster. This thesis has shown that this effect does not extend to effecting memory performance. The number of papillae does not relate to memory performance. Levels of processing, which was the most influential theory and methodological framework of memory during the last century was applied to taste for the first time in this PhD. The theory states that memory is dependent on the depth of processing. The first study used liking (deep) and pulpiness (shallow) as orientating tasks. The second study used liking by a significant other (deepest), liking (deep) and sip size as orientating tasks. Despite best efforts no LOP effect could be found for flavour using orange juice as the stimuli the issue of power was identified as a substantial caveat to this conclusion. The second half of the thesis investigated whether there was a CP effect for flavour and whether the traditional CP account, or Shift Toward Prototype (STP) or 4 Perceptual Magnet theory could account for the effect. A categorical perception effect for flavour was indentified in all three binary tastant mixtures, comprising mixtures of orange, lemon or blackcurrant. The effect was replicated three times for the orange-lemon tastant mixtures. A ‘prototype effect’ was also identified at the orange, lemon and blackcurrant 100% concentrations. The pattern of results at the prototype resembled the pattern at the category boundary. This does not support perceptual magnet theory. It may support novel tastant detection as demonstrated by Mojet and Koste (2005). While there was evidence for a CP effect this seemed to diminish with time. This contradicted the STP account. The role of memory is given consideration and the idea of prototypes in the studies is evaluated. A critical evaluation of the research and possible future directions are included. Contents University of Surrey .................................................................................................1 Acknowledgements .............................................................................................................3 Abstract..................................................... 4 Contents ...............................................................................................................................6 Section One ..........................................................................................................................9 Chapter One: Introduction ..................................................................................................9 Food choice and the psychology of eating ....................................................................9 A gap in our understanding .......................................................................................... 13 Understanding the role of cognition in the psychology of eating ............................. 20 Aims...............................................................................................................................20 Focus..............................................................................................................................20 Structure ........................................................................................................................ 21 Chapter Two: Beyond Sensation .....................................................................................25 Anatomy and physiology ............................................................................................. 26 The taste organs and papillae power ........................................................................... 27 The brain’s control of eating ........................................................................................29 Sensation and perception ............................................................................................. 38 The role of memory in the psychology of eating ....................................................... 44 Theory in mind: the origins of memory theories ....................................................... 49 Levels of processing (LOP)......................................................................................... 50 Limits and latitudes of levels of processing ................................................................54 The STM/LTM distinction and the demise of the modal model .............................. 57 Consolidation is crucial ................................................................................................ 59 The obscure and mysterious index of depth ...............................................................60 Visualising depth: neuro-imaging and physiological measures of depth .................62 The reality and nature of levels ....................................................................................65 General to specific levels of representation ................................................................67 Transfer appropriate processing (TAP), Encoding-retrieval interactions .................68 The relationship between LOP & TAP and the troubling tautology ......................... 69 Levels of Processing: Synopsis ....................................................................................74 Chapter Three: Aim and purpose .....................................................................................77 Section 2: Levels of processing .......................................................................................81 Chapter Four......................................................................................................................81 Section overview ...........................................................................................................81 Levels of processing and papillae ................................................................................82 Study one: Depth of Processing and Papillae Density