Browsing by Subject "Experimental psychology"
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Item Open Access Context-Specific Adjustments of Cognitive Flexibility(2023) Siqi-Liu, AudreyThe stability-flexibility dilemma describes the challenge of balancing the antagonistic goals of focusing on the current task-set (cognitive stability) and updating that task-set in response to changes in the environment (cognitive flexibility). Dynamic adjustments of cognitive flexibility are observed in cued task-switching paradigms, wherein switch costs, or the performance costs associated with switching between tasks, have been shown to decrease as the proportion of switch trials within a block increase. This effect is referred to as the list-wide proportion switch (LWPS) effect, and presents evidence of meta-flexibility, or people’s ability to find an optimal level of flexibility based on contextual demands. While context-sensitive control adaptations have been extensively researched in the conflict literature, fewer studies have been dedicated to investigating such flexibility adaptations. Consequently, the underlying mechanisms of meta-flexibility remain unknown. Across four behavioral experiments, Chapter 2 teases apart the different levels of learning that may contribute to list-wide flexibility adaptations, controlling for stimulus- and task-level associations. Chapter 3 investigates the EEG neural signatures of meta-flexibility. In Chapter 4, we test for whether learned flexibility adjustments benefit from memory consolidation, like other forms of associative learning. Lastly, Chapter 5 utilized three novel behavioral paradigms to investigate different conditions under which flexibility learning transfers or fails to transfer. Collectively, the results in this dissertation suggest that flexibility adjustments to contextual demands occurs rapidly and transfers reliably across novel stimuli, such that, in high switch frequency blocks, participants could perform more rapid task switches even on trials involving items never seen before. However, both behavioral and neural evidence suggest that flexibility learning is also task specific, such that switch performance boosts to tasks that appear more often as switch trials do not generalize to other tasks that occur in the same temporal contexts.
Item Open Access Does our perception of animals shape when we see all humans as being created equally?(2022) Zhou, WenHumans are paradoxical in their ability for extreme kindness and cruelty. The goal of this dissertation is to further uncover the psychological mechanism(s) that allow humans to accept harm directed at members of other groups. The human self-domestication hypothesis proposes that human unique forms of mentalizing evolved as a byproduct of selection for ingroup prosociality. Hare (2017) proposed that late in human evolution Homo sapiens bonded more closely with ingroup members and more skillfully read the mental states of others. Moral and cultural behaviors expanded, and modern human behavior emerged. However, more closely bonded groups tend to perceive outgroup strangers as more threatening. It became advantageous to deny some forms of human-unique mental states to individuals from threatening groups. In this way emotional and moral constraints on violence toward other humans can be escaped. The potential for lethal aggression and harm toward outgroup strangers became even more extreme as a result. According to this model there should be strong psychological links between group identity, mental state attribution, moral exclusion, and a willingness to harm others. Two main mechanisms have been proposed to provide this link. The first is dehumanization or the ability to deny fully human emotions and mental abilities to another person or group of people (Haslam, 2006). The second is social dominance orientation or the perception of a hierarchy between different human groups (Sidanius & Pratto, 2001). Together these mechanisms can override individual characteristics that lead to concern. Group identity alone can be used to indicate inferiority or less than human status. Moral exclusion and harm can follow. More recently a third moderating factor has been proposed. Costello & Hodson (2010) proposed that beliefs about animals strongly shape tendencies to dehumanize. Seeing animals as having human-like minds negates the negative impact of dehumanization since being nonhuman is so similar to being human. In Chapter 1, I combine this evolutionary model with the proposed mechanisms that drive the worst forms of group-based aggression to propose the Dehumanization of Inferior Groups (DIG) Hypothesis. The DIG hypothesis suggests the perception of other groups of humans is strongly modulated by how we view the minds of other animals, their relationship with each other and our relationship to them. Our minds evolved to distinguish between humans and animals, but we develop the ability to categorize some members of our own species as more animal-like. We also evolved to categorize the relative equality or inequality of different groups. This includes groups of animals that can be perceived as different but equal or ranked hierarchically. How we perceive different groups of animals will relate to how hierarchically we view different groups within our own species. The present dissertation seeks to provide initial tests of the DIG hypothesis. To do so, I used experiment-based surveys, investigating behavioral patterns of adults and school age children. In Chapter 2, I assessed dehumanizing tendency in adults and children, revealing that variety of humanness representations can elicit dehumanization in both age groups. Similar to the links seen in previous investigations of adults, children’s willingness to dehumanize is related to their acceptance that other groups can be inferior and more deserving of punishment. In Chapter 3, I examined the association between the perception of animal-to-human similarity and dehumanization. Results in adults and children showed that highlighting mental similarities between animals and humans could narrow down the perceived animal-human divide. However, in both age group, this manipulation does not attenuate dehumanization or the intergroup biases associated with it. Chapter 4 explored the association between the treatment of other human groups and the treatment of animals in a variety of participants who were engaged in different relationship with animals. I found that people who endorsed discrimination of dog breeds also endorsed group-based discrimination in human society. Moreover, positive contact with dogs is associated with disapproval of group-based inequality. Together, these findings suggest that the perception of human intergroup relations and the perception of relationship among animal groups are dependent upon similar cognitive processes. The studies presented here have implications for understanding psychological origins of dehumanization as well as designing interventions to promote intergroup tolerance.
Item Open Access Expressive Control and Emotion Perception: the Impact of Expressive Suppression and Mimicry on Sensitivity to Facial Expressions of Emotion(2008-05-28) Schneider, Kristin GraceRecent studies have linked expressive suppression to impairments in interpersonal functioning, but the mechanism underlying this relationship has not been well articulated. One possibility is that the individual who engages in expressive suppression is impaired in perceiving the emotions of others, a critical ability in successful interpersonal functioning. In the current study, participants were presented with a series of photographs of facial expressions that were manipulated so that they appeared to "morph" from neutral into full emotion expressions. As they viewed these images, participants were instructed to identify the expression as quickly as possible, by selecting one of the six emotion labels (happiness, sadness, fear, anger, surprise, and disgust) on the screen. Prior to this task, participants were randomized to one of three groups: instructed to mimic the expressions on the screen, instructed to suppress all emotion expressions, or not given specific instructions on how to control expressions (the control group). The speed with which participants accurately identified emotional expressions (emotion sensitivity) was the primary variable of interest. Overall, participants in the suppression condition were found to be slower to accurately identify emotions, while no statistically-significant differences were found between the mimicry and no-instructions conditions. The decreased emotion sensitivity in the suppression group could not be accounted for by impulsive responding, decreased sensitivity at full expression, or perceived difficulty of task.
Item Open Access Feeling Good and Doing Better: How Specific Positive Emotions Influence Consumer Behavior and Well-being(2009) Cavanaugh, Lisa AnnMarketers seek to create and consumers seek to cultivate a variety of positive emotional experiences. Despite their importance to consumer behavior, researchers have lacked a clear understanding of the distinct behavioral consequences of specific positive emotions. My dissertation examines how different positive emotions (e.g., hope, love, and pride) can differentially affect consumers' decisions and behaviors. I find that positive emotions can not only be differentiated but also that specific positive emotions lead to distinctly different patterns of consumption behavior, such as considering more options, donating in different ways, engaging in more effortful actions, or performing more socially conscious consumption behaviors benefiting distant others. I find important differences both with momentary emotional experiences and downstream consequences of chronic emotional experiences.
Positive emotions differ reliably in the degree to which they create a lens of problem-solving, social connection, and perceived control. For example, I find that positive emotions characterized by a social connection lens (e.g., love and gratitude) lead to increases in socially conscious behaviors benefiting distant others. The tendency to perceive one's environment through a problem-solving lens (which characterizes hope and interest but not love and gratitude) leads to larger consideration sets and engagement in more effortful environmental actions. I also examine how positive emotions characterized by different lenses, such as perceived control (e.g., pride) and social connection (e.g., love), produce distinct behaviors within the same consumption context (e.g., giving in different ways in response to a fundraising appeal). Five studies demonstrate that positive emotions can be characterized in ways that allow prediction of distinct forms of broadening and specific consumption behaviors.
Item Open Access Integrating Channels of Emotion: Individual Differences in Subjective Experience, Psychophysiology and Neural Activity(2021) Burr, Daisy AlmaEmotions infuse each individual’s life with meaning, informing their memories and guiding their future decisions. Previous research has emphasized three important channels of emotion: subjective experience, psychophysiology and neural activity. In addition, research has found that individuals manage their emotions across channels in a diversity of ways. However, most of this research narrowly focuses on a single channel of emotion and misses key aspects of these individual differences. Across 4 studies, this dissertation highlights the immense variability in emotional experiences by integrating channels of emotion. The first empirical chapter (Chapter 2) focuses on subjective channels of emotion and reveals a fundamental aspect of emotion previously unknown—that positive events are actually less complex than negative events, and that individuals evaluate positive events more similarly than negative events. The next chapter (Chapter 3) uses a novel computational approach to identify a whole-brain biomarker of the tendency to suppress negative emotion. The following chapter (Chapter 4) focuses on psychophysiological channels of emotion and investigates the effect of anxiety on how individuals manage their emotions naturally versus when following instructions in the laboratory. Participants report managing their emotions in ways that did not did not reflect how they regulated in the lab—highlighting the importance of conducting research outside the laboratory. Based on this, the final empirical chapter (Chapter 5) uses experience sampling to leave the confines of the laboratory and study people in the wild. Participant responses show that multiple components of emotional health improve with age, including emotional stability, affect, and the ability to resist desire—a finding missing from laboratory-based research. No two individuals are alike in how they experience and manage their emotions. This research emphasizes the vast variability in how individuals experience and manage emotion depending on their goals and the larger context. This holistic framework enhances our understanding of the full spectrum of emotional functioning and brings the field closer to a personalized account of emotion.
Item Open Access Mechanisms by Which Early Nutrition Influences Spatial Memory, Adult Neurogenesis, and Response to Hippocampal Injury(2010) Wong-Goodrich, Sarah Jeanne EvensAltered dietary availability of the vital nutrient choline during early development leads to persistent changes in brain and behavior throughout adulthood. Prenatal choline supplementation during embryonic days (ED) 12-17 of the rodent gestation period enhances memory capacity and precision and hippocampal plasticity in adulthood, and protects against spatial learning and memory deficits shortly after excitotoxic seizures, whereas prenatal choline deficiency can compromise hippocampal memory and plasticity in adulthood. Recent evidence from our laboratory has determined that lifelong proliferation of newborn neurons in the adult hippocampus, a feature of adult hippocampal plasticity that has been implicated in some aspects of learning and memory, is modulated by early choline availability. Prenatal choline's effects on adult neurogenesis may be one mechanism for diet-induced cognitive changes throughout life and in response to injury, although little is known about the mechanisms underlying how prenatal choline alters adult neurogenesis or the neural mechanisms underlying prenatal choline supplementation's protection against cognitive deficits after seizures. To address these issues, the present set of experiments investigated how prenatal choline availability modulates specific properties of neurogenesis in the adult brain (in the intact brain and in response to injury), as well as hippocampal markers known to change in response to excitotoxin-induced seizures, and sought to relate changes in neurogenesis and in neuropathological markers following injury to changes in performance on spatial learning and memory tasks. Subjects in each experiment were adult offspring from rat dams that received either a control diet or diet supplemented with choline chloride or deficient of choline on ED 12-17. To measure neurogenesis, rats were given injections of the mitotic marker bromodeoxyurdine to label dividing cells in the hippocampus. Prenatal choline supplementation enhanced several properties of basal adult hippocampal neurogenesis (cell division and survival, neural stem/progenitor cell phenotype and proliferative capacity, trophic support), and this increase was associated with improvements in spatial working memory retention in a delayed-matching-to-place water maze task. In contrast, prenatal choline deficiency had little effect on basal adult hippocampal neurogenesis, and no effect on spatial memory performance. Prenatal choline supplementation also enhanced olfactory bulb neurogenesis without altering cell proliferation in the subventricular zone, while prenatal choline deficiency had no effect on either measure, showing for the first time that prenatal choline's effects on adult neurogenesis is similarly expressed in another distinct neurogenic region of the adult brain. Altered prenatal choline availability also modulated the hippocampal response to kainic acid-induced seizures where supplementation attenuated while deficiency had no effect on the injury-induced proliferative response of the dentate gyrus shortly after injury. Prenatal choline supplementation also attenuated other markers of hippocampal neuropathology shortly after seizures and promoted the long-term hippocampal recovery from seizures months after injury, including rescuing declines in adult hippocampal neurogenesis and in spatial memory performance in a standard water maze task. Taken together, these findings demonstrate a robust neuroprotective effect of prenatal choline supplementation that may be driven by enhanced adult hippocampal plasticity and trophic support prior to injury, and shed light on the mechanisms underlying how prenatal choline availability alters adult hippocampal neurogenesis, which may contribute to changes in memory capacity and precision both throughout life and following neural assault.
Item Open Access Neural Coding Strategies in Cortico-Striatal Circuits Subserving Interval Timing(2010) Cheng, Ruey-KuangInterval timing, defined as timing and time perception in the seconds-to-minutes range, is a higher-order cognitive function that has been shown to be critically dependent upon cortico-striatal circuits in the brain. However, our understanding of how different neuronal subtypes within these circuits cooperate to subserve interval timing remains elusive. The present study was designed to investigate this issue by focusing on the spike waveforms of neurons and their synchronous firing patterns with local field potentials (LFPs) recorded from cortico-striatal circuits while rats were performing two standard interval-timing tasks. Experiment 1 demonstrated that neurons in cortico-striatal circuits can be classified into 4 different clusters based on their distinct spike waveforms and behavioral correlates. These distinct neuronal populations were shown to be differentially involved in timing and reward processing. More importantly, the LFP-spike synchrony data suggested that neurons in 1 particular cluster were putative fast-spiking interneurons (FSIs) in the striatum and these neurons responded to both timing and reward processing. Experiment 2 reported electrophysiological data that were similar with previous findings, but identified a different cluster of striatal neurons - putative tonically-active neurons (TANs), revealed by their distinct spike waveforms and special firing patterns during the acquisition of the task. These firing patterns of FSIs and TANs were in contrast with potential striatal medium-spiny neurons (MSNs) that preferentially responded to temporal processing in the current study. Experiment 3 further investigated the proposal that interval timing is subserved by cortico-striatal circuits by using microstimulation. The findings revealed a stimulation frequency-dependent "stop" or "reset" response pattern in rats receiving microstimulation in either the cortex or the striatum during the performance of the timing task. Taken together, the current findings further support that interval timing is represented in cortico-striatal networks that involve multiple types of interneurons (e.g., FSIs and TANs) functionally connected with the principal projection neurons (i.e., MSNs) in the dorsal striatum. When specific components of these complex networks are electrically stimulated, the ongoing timing processes are temporarily "stopped" or "reset" depending on the properties of the stimulation.
Item Open Access Object-Directed Action Experiences and their Effect on Cognitive and Social Development(2010) Libertus, KlausReaching is an important and early emerging motor skill that allows infants to interact with the physical and social world (e.g., when sharing objects). Despite the importance of motor experiences in early infancy, few studies have considered the influence of reaching behavior on cognitive, social, and motor development. In this dissertation, reaching behavior was selectively manipulated in 73 non-reaching three-month-old infants using four different training interventions. Infants' reaching and social cognition skills were assessed and compared, and the long-term effects of one particular training intervention were explored.
Of the four training interventions used here, one procedure--referred to as active training--facilitated domain-specific development (reaching and grasping behavior) and increased infants' preferential orienting towards faces in a visual-preference task (face preference). None of the remaining three training interventions facilitated motor development and only one increased face-preference behavior. However, a relation between face-preference behavior and motor experience was present in all trained infants as well as in three- to 11-month-old untrained infants. In untrained infants, face-preference behavior was the earliest social-cognition skill to emerge and was related to later emerging skills such as gaze following. Therefore, a preference for faces may be an important basic social-cognition skill that influences future social development.
Additionally, the long-term effects of the active-training procedure were assessed in 14 infants who were tested one year after they had participated in the active-training intervention. Even after one year, converging evidence showed advanced manual exploration and object-engagement skills in trained compared to untrained infants.
The studies described in this dissertation attempt to systematically investigate the role of early reaching experiences on subsequent development of motor and social cognition behaviors. The present findings demonstrate the importance of self-produced motor experiences on the development of social cognition and have implications for our understanding of typical development and the etiology of developmental disorders in social cognition.
Item Open Access Social Decision-Making in Bonobos and Chimpanzees(2016) Krupenye, ChristopherHumans are natural politicians. We obsessively collect social information that is both observable (e.g., about third-party relationships) and unobservable (e.g., about others’ psychological states), and we strategically employ that information to manage our cooperative and competitive relationships. To what extent are these abilities unique to our species, and how did they evolve? The present dissertation seeks to contribute to these two questions. To do so, I take a comparative perspective, investigating social decision-making in humans’ closest living relatives, bonobos and chimpanzees. In Chapter 1, I review existing literature on theory of mind—or the ability to understand others’ psychological states—in these species. I also present a theoretical framework to guide further investigation of social cognition in bonobos and chimpanzees based on hypotheses about the proximate and ultimate origins of their species differences. In Chapter 2, I experimentally investigate differences in the prosocial behavior of bonobos and chimpanzees, revealing species-specific prosocial motivations that appear to be less flexible than those exhibited by humans. In Chapter 3, I explore through decision-making experiments bonobos’ ability to evaluate others based on their prosocial or antisocial behavior during third-party interactions. Bonobos do track the interactions of third-parties and evaluate actors based on these interactions. However, they do not exhibit the human preference for those who are prosocial towards others, instead consistently favoring an antisocial individual. The motivation to prefer those who demonstrate a prosocial disposition may be a unique feature of human psychology that contributes to our ultra-cooperative nature. In Chapter 4, I investigate the adaptive value of social cognition in wild primates. I show that the recruitment behavior of wild chimpanzees at Gombe National Park, Tanzania is consistent with the use of third-party knowledge, and that those who appear to use third-party knowledge receive immediate proximate benefits. They escape further aggression from their opponents. These findings directly support the social intelligence hypothesis that social cognition has evolved in response to the demands of competing with one’s own group-mates. Thus, the studies presented here help to better characterize the features of social decision-making that are unique to humans, and how these abilities evolved.
Item Open Access The Characteristics and Neural Substrates of Feedback-based Decision Process in Recognition Memory(2008-04-10) Han, SanghoonThe judgment of prior stimulus occurrence, generally referred to as item recognition, is perhaps the most heavily studied of all memory skills. A skilled recognition observer not only recovers high fidelity memory evidence, he or she is also able to flexibly modify how much evidence is required for affirmative responding (the decision criterion) depending upon whether the context calls for a cautious or liberal task approach. The ability to adaptively adjust the decision criterion is a relatively understudied recognition skill, and the goal of this thesis is to examine reinforcement learning mechanisms contributing to recognition criterion adaptability. In Chapter 1, I review a measurement model whose theoretical framework has been successfully applied to recognition memory research (i.e., Signal Detection Theory). I also review major findings in the recognition literature examining the adaptive flexibility of criteria. Chapter 2 reports behavioral experiments that examine the sensitivity of decision criteria to trial-by-trial feedback by manipulating feedback validity in a potentially covert manner. Chapter 3 presents another series of behavioral experiments that used even subtler feedback manipulations based on predictions from reinforcement learning and category learning literatures. The findings suggested that feedback induced criterion shifts may rely upon procedural learning mechanisms that are largely implicit. The data also revealed that the magnitudes of induced criterion shifts were significantly correlated with personality measures linked to reward seeking outside the laboratory. In Chapter 4 functional magnetic resonance imaging (fMRI) was used to explore possible neurobiological links between brain regions traditionally linked to reinforcement processing, and recognition decisions. Prominent activations in striatum tracked the intrinsic goals of the subjects with greater activation for correct responding to old items compared to correct responding to new items during standard recognition testing. Furthermore, the pattern was amplified and reversed by the addition of extrinsic rewards. Finally, activation in ventral striatum tracked individual differences in personality reward seeking measures. Together, the findings further support the idea that a reinforcement learning system contributes to recognition decision-making. In the final chapter, I review the main implications arising from the research and suggest future research that could bolster the current results and implications.Item Open Access The Impact of Skill-based Training Across Different Levels of Autonomy for Drone Inspection Tasks(2018) Kim, MinwooGiven their low operating costs and flight capabilities, Unmanned Aircraft Vehicles(UAVs), especially small size UAVs, have a wide range of applications, from civilian rescue missions to military surveillance. Easy control from a highly automated system has made these compact UAVs particularly efficient and effective devices by alleviating human operator workload. However, whether or not automation can lead to increased performance is not just a matter of system design but requires operators’ thorough understanding of the behavior of the system. Then, a question arises: which type of training and level of automation can help UAV operators perform the best?
To address this problem, an experiment was designed and conducted to compare the differences in performance between 3 groups of UAV operators. For this experiment, 2 different interfaces were first developed - Manual Control, which represents low LOA interface, and Supervisory Control, which represents high LOA interface - and people were recruited and randomly divided into 3 groups. Group 1 was trained using Manual Control, and Group 3 was trained using Supervisory Control while Group 2 was trained using both Manual and Supervisory Control. Participants then flew a drone in the Test Mission stage to compare performance.
The results of the experiment were rather surprising. Although group 3 outperformed group 1, as expected, the poor performance of group 2 was unexpected and gave us new perspectives on additional training. That is, additional training could lead not just to a mere surplus of extra skills but also a degradation of existing skills. An extended work using a more mathematical approach should allow for a more precise, quantitative description on the relation between extra training and performance.
Item Open Access Two Essays on Escalation of Commitment(2009) Guha, AbhijitThis dissertation focuses on managerial decision making, and specifically explores conditions wherein managers may increase their propensity to escalate commitment towards a failing project. Escalation researchers (e.g. Schmidt and Calantone, 2002) have listed four classes of factors that may impact a manager's propensity to escalate commitment towards a failing project, and have called for research into how exactly these factors impact escalation. In this dissertation, we explore two such factors. The first factor relates to the characteristics of the decision process used by firms to evaluate the project. Here, for example, researchers have looked at whether the manager was also involved in making decisions about the project in a prior period, and Boulding, Morgan and Staelin (1997) have shown that such manager's positive beliefs about the project (formed in a prior period) make a manager more likely to escalate commitment. The second factor relates to project characteristics. Here, for example, researchers have looked at whether or not the project relates to a product that is perceived as new, and Schmidt and Calantone (2002) have shown that managers are more likely to escalate commitment towards a failing project relating to a new product.
The first dissertation essay uses three experiments to examine how a hitherto unexplored characteristic of the decision process might lead to increasing escalation of commitment. Specifically, building off research into the illusion of control, we examine whether the opportunity to use managerial skill during the decision process makes a manager more willing to escalate commitment towards a failing project. We find that whenever managers act on cues that cause them to think they can use their managerial skill to control some outside factor (even though in reality they cannot), managers overestimate their ability to "control the odds" related to this outside factor. Such beliefs feed forward and lead managers to make suboptimal decisions about the overall project.
The second dissertation essay looks at how project characteristics might make a manager more (or less) likely to escalate commitment towards a failing project. We explore this issue in the hitherto unexplored real options setting. Real options have emerged as an important part of marketing strategy, and have been used to structure new product alliances, value customers etc. We run a controlled experiment and we examine whether differences in option-structure (which is a project characteristic) impact the propensity to make suboptimal option-exercise decisions. We find that managers are more likely to make suboptimal option-exercise decisions in the case of put options (vis. call options), and - as predicted by the endowment effect literature - this increased propensity to make a suboptimal decision is mediated by/ explained by the psychological ownership construct.
Item Open Access What Makes Our Minds Human? Comparative Phylogenetic Perspectives on the Evolution of Cognition(2012) MacLean, EvanWhat makes our minds human? How did they evolve to be this way? This dissertation presents data from two complementary lines of research driven by these orienting questions. The first of these explores the `what' of human cognitive evolution through comparative studies with chimpanzees and bonobos. The general aim of these studies is to understand which aspects of cognition are unique to humans, and which are shared with our closest living relatives. Chapters 2-3 test the hypothesis that humans have unique cognitive skills for reasoning about the attention of other individuals (theory of mind), and unique motivation to use these skills in cooperative contexts with conspecifics. In Chapter 2 I show that understanding others' attention is unlikely to be the `small difference that makes the big difference', as some researchers have proposed. However, my data support the possibility that species differences in the ontogeny of these skills may have robust consequences for the adult cognitive phenotype. In Chapter 3 I show that (contrary to previous reports) nonhuman apes are also motivated to engage in some simple triadic social activities, which resemble those characteristic of human children. Again however, I identify important differences between humans and other apes in their spontaneous preferences for these types of activities, and their attitudes toward a partner when cooperative behaviors are interrupted. The second half of this dissertation (Chapters 4-5) explores the `why' and `how' of cognitive evolution. Chapter 4 outlines the kind of research questions and methods that comparative psychologists will need to embrace in order to use the comparative method to its full potential in the study of cognitive evolution. Chapter 5 provides a proof of principle for this approach using a dataset including 33 species tested on two cognitive tasks measuring inhibitory control. Here I show that cognitive skills for inhibitory control are closely related to phylogeny across species, and strongly predicted by absolute (but not relative) brain size. Further, I show that two of the other leading hypotheses put forth to explain primate intelligence, namely sociality and diet, do not predict cognitive skills on these tasks. These data illustrate the power of the comparative method for understanding cognitive evolution, and provide a starting point for future studies embracing this approach. Collectively, this research refines our understanding of how human cognition differs from that of other primates, and illustrates the utility of studying cognitive evolution from an explicitly phylogenetic comparative framework.