The Psychology and Evolution of Foraging Skills in Primates by Alexandra Rosati Department of ...

254 Pages·2012·9.95 MB·English

by  Alexandra Rosati

The Psychology and Evolution of Foraging Skills in Primates
by
Alexandra Rosati
Department of Evolutionary Anthropology
Duke University

Date:_______________________
Approved:

___________________________
Brian Hare, Supervisor

___________________________
R. Alison Adcock

___________________________
Kenneth Glander

___________________________
Richard Kay

___________________________
Anne Pusey

Dissertation submitted in partial fulfillment of
the requirements for the degree of Doctor
of Philosophy in the Department of
Evolutionary Anthropology in the Graduate School
of Duke University

2012
ABSTRACT
The Psychology and Evolution of Foraging Skills in Primates
by
Alexandra Rosati
Department of Evolutionary Anthropology
Duke University

Date:_______________________
Approved:

___________________________
Brian Hare, Supervisor

___________________________
R. Alison Adcock

___________________________
Kenneth Glander

___________________________
Richard Kay

___________________________
Anne Pusey

An abstract of a dissertation submitted in partial
fulfillment of the requirements for the degree
of Doctor of Philosophy in the Department of
Evolutionary Anthropology in the Graduate School of
Duke University

2012
Copyright by
Alexandra Rosati
2012
Abstract
Primates in the wild face complex foraging decisions where they must assess the
most valuable of different potential resources to exploit, as well recall the location of
options that can be widely distributed. While differences in diet and ecology have long
been thought to be an important factor influencing brain evolution in primates, it is less
well understood what psychological abilities animals actually use when making foraging
decisions. This dissertation examines cognitive domains that play a crucial role in
supporting foraging behaviors—spatial memory and decision-making—by integrating
both psychological and biological approaches to behavior. In particular, the research
presented here examines multiple species of primates to address the cognitive skills that
different animals use to solve foraging problems (at the proximate level of analysis), as
well as why some species appear to solve such problems differently than other species
(at the ultimate level of analysis).
The first goal of the dissertation is to compare closely-related species that vary in
ecological characteristics, in order to illuminate how evolution shapes the cognitive
skills used in foraging contexts. This component focuses on comparisons between
chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), humans’ closest extant
relatives. In addition, this component reports comparisons amongst strepsirrhines
(Lemur catta, Eulemur mongoz, Propithecus coquereli, and Varecia subsp.) to model cognitive
evolution in a taxonomic group with greater ecological diversity than Pan. The first two
chapters test the hypothesis that more frugivorous species exhibit more accurate spatial
memory skills, first by comparing apes’ spatial memory abilities (Chapter 2), and then
by comparing four species of lemurs on a related set of spatial memory tasks (Chapter
3). In subsequent chapters, I examine apes’ decision-making strategies to test the
hypothesis that chimpanzees are more willing to pay decision-making costs than are
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bonobos, due to differences in their feeding ecology. I focus on preferences about the
timing of payoffs (Chapter 4); preferences about risk, or the variability in payoffs
(Chapters 4 and 5); and preferences about ambiguity, or knowledge about available
options (Chapter 6).
The second goal of the dissertation is to compare the psychological mechanisms
that human and nonhuman great apes use for foraging, in order to identify potentially
human-unique cognitive abilities. In terms of spatial memory, I examine whether other
apes also exhibit human-like patterns of spatial memory development (Chapter 2). In
terms of decision-making, I examine whether apes exhibit a suite of human-like biases
when making value-based choices. In particular, I test whether emotional and
motivational processes, which are critical components of human decision-making, also
play a role in apes’ choices (Chapters 4); whether apes are sensitive to social context
when making economic decisions (Chapter 5); and whether apes are sensitive to their
degree of knowledge when making choices under uncertainty (Chapter 6). Finally, I
directly compare human and ape preferences on a matched task to assess whether
humans use any unique psychological abilities when making decisions about risk
(Chapter 7). In sum, this dissertation links studies of mechanism with hypotheses about
function in order to illuminate the evolutionary roots of human's unique cognitive
phenotype.

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Contents
Abstract..........................................................................................................................................iv

List of Tables...............................................................................................................................xiii

List of Figures..............................................................................................................................xv

Acknowledgements.................................................................................................................xviii

1. Introduction...............................................................................................................................1

1.1 Theoretical approaches to cognitive evolution............................................................1

1.2 The ecological intelligence hypothesis..........................................................................3

1.3 Target cognitive skills......................................................................................................6

1.3.1 Spatial memory: locating resources..........................................................................7

1.3.1.1 Psychological and neurobiological substrates for memory...........................8

1.3.1.2 Previous comparative work on memory..........................................................9

1.3.2 Value-based decision-making: resource tradeoffs................................................12

1.3.2.1 Psychological and neurobiological substrates for decision-making..........13

1.3.2.2 Previous comparative work on decision-making.........................................17

1.4 Focus species...................................................................................................................19

1.4.1 Chimpanzees and bonobos: the origins of human cognition.............................19

1.4.2 Strepsirrhines: modeling the evolution of foraging skills...................................22

1.4.3 Humans: cognition for foraging..............................................................................23

1.5 Research goals.................................................................................................................25

2. Spatial memory in apes..........................................................................................................27

2.1 Background: spatial memory development...............................................................27

2.2 Study 1: Memory in a naturalistic foraging context..................................................31

2.2.1 Methods......................................................................................................................31

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2.2.1.1.Subjects................................................................................................................31

2.2.1.2. Procedure...........................................................................................................32

2.2.1.3 Data coding and analysis..................................................................................34

2.2.2 Results.........................................................................................................................34

2.3 Study 2: Reducing memory demands.........................................................................39

2.3.1 Methods......................................................................................................................40

2.3.1.1. Subjects...............................................................................................................40

2.3.1.2 Procedure............................................................................................................40

2.3.1.3 Data coding and analysis..................................................................................41

2.3.2 Results.........................................................................................................................41

2.4 Study 3: Memory choice task........................................................................................43

2.4.1 Methods......................................................................................................................44

2.4.1.1 Subjects................................................................................................................44

2.4.1.2 Pretest procedure...............................................................................................44

2.4.1.3 Test procedure....................................................................................................45

2.4.1.4 Data coding and analysis..................................................................................47

2.4.2 Results.........................................................................................................................47

2.5 Discussion........................................................................................................................49

3. Spatial memory in lemurs......................................................................................................55

3.1 Background: memory evolution...................................................................................55

3.2 Study 1: Memory after a long delay.............................................................................58

3.2.1 Methods......................................................................................................................58

3.2.1.1 Subjects................................................................................................................58

3.2.1.2 General setup and apparatus...........................................................................58

3.2.1.3 Sessions................................................................................................................60

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3.2.1.4 Trial procedure...................................................................................................60

3.2.1.5 Data coding and analysis..................................................................................61

3.2.2 Results.........................................................................................................................61

3.3 Study 2: Mechanisms for memory...............................................................................64

3.3.1 Methods......................................................................................................................64

3.3.1.1 Subjects................................................................................................................64

3.3.1.2 General setup and apparatus...........................................................................65

3.3.1.3 Sessions................................................................................................................65

3.3.1.4 Trial procedure...................................................................................................65

3.3.1.5 Data coding and analysis..................................................................................66

3.3.2 Results.........................................................................................................................66

3.4 Study 3: Memory for multiple locations.....................................................................69

3.4.1 Methods......................................................................................................................69

3.4.1.1 Subjects................................................................................................................69

3.4.1.2 General setup and apparatus...........................................................................69

3.4.1.3 Session phases and procedure.........................................................................70

3.4.1.4 Data coding and analysis..................................................................................70

3.4.2 Results.........................................................................................................................71

3.5 Discussion........................................................................................................................74

4. Preferences for time and risk in apes...................................................................................77

4.1 Background: decision-making and emotion...............................................................77

4.2 Study 1: Temporal preferences.....................................................................................82

4.2.1 Methods......................................................................................................................82

4.2.1.1 Subjects................................................................................................................82

4.2.1.2 Quantity discrimination pretest.......................................................................83

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4.2.1.3 Temporal choice procedure..............................................................................83

4.2.1.4 Apes’ responses and coding............................................................................85

4.2.1.5 Data coding and analysis..................................................................................86

4.2.2 Results.........................................................................................................................86

4.2.2.1 Quantity discrimination pretest.......................................................................86

4.2.2.2 Temporal choices...............................................................................................86

4.2.2.3 Emotional and motivational responses..........................................................87

4.3 Study 2: Risk preferences..............................................................................................90

4.3.1 Methods......................................................................................................................90

4.3.1.1 Subjects................................................................................................................90

4.3.1.2 Food preference pretest.....................................................................................91

4.3.1.3 Risky choice procedure.....................................................................................91

4.3.1.4 Control trials......................................................................................................93

4.3.1.5 Apes’ responses and coding.............................................................................95

4.3.2 Results.........................................................................................................................95

4.3.2.1 Food preferences................................................................................................95

4.3.2.2 Control trials.......................................................................................................96

4.3.2.3 Risk preferences.................................................................................................97

4.3.2.4 Emotional and motivational responses..........................................................98

4.4 Discussion......................................................................................................................104

5. Preferences for risk across social context in apes.............................................................109

5.1 Background: decision-making and social context...................................................109

5.2 Study 1: Influence of a competitive context..............................................................114

5.2.1 Methods....................................................................................................................115

5.2.1.1 Subjects..............................................................................................................115

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5.2.1.2 General set-up and risky choice task............................................................115

5.2.1.3 Food preference pretest...................................................................................117

5.2.1.4 Risk introduction session and control trials.................................................118

5.2.1.5 Test sessions and competition procedure.....................................................119

5.2.1.6 Data coding and analysis................................................................................121

5.2.2 Results.......................................................................................................................122

5.2.2.1 Food preference pretest...................................................................................122

5.2.2.2 Control trials and reward history..................................................................123

5.2.2.3 Risk preferences...............................................................................................124

5.3 Study 2: Influence of a play context...........................................................................128

5.3.1 Methods....................................................................................................................128

5.3.1.1 Subjects..............................................................................................................128

5.3.1.2 Procedure..........................................................................................................129

5.3.2 Results.......................................................................................................................129

5.3.2.1 Control trials and reward history..................................................................129

5.3.2.2 Risk preferences...............................................................................................130

5.3.2.3 Comparison of studies 1 and 2.......................................................................132

5.4 Discussion......................................................................................................................133

6. Preferences for ambiguity in apes......................................................................................138

6.1 Background: decision-making and knowledge.......................................................138

6.2 Methods.........................................................................................................................140

6.2.1 Subjects......................................................................................................................140

6.2.2 Procedure..................................................................................................................140

6.2.2.1 Risky choice task..............................................................................................141

6.2.2.2 Session structure..............................................................................................142

x