An Investigation of Emergent Perceptual Phenomena in Primates: Illusions and Biases in Decision-Making

The perceptual system operates ideally to reveal rapidly processed, accurate and functional information to an organism. However, illusory phenomena emerge when there is discontinuity between sensory input and perception on the basis of misleading contexts. Because illusions emerge as a byproduct of an otherwise functional and efficient perceptual system, they provide a means to understand better mechanisms of perception within and across species. Beyond anatomical and functional similarities in the visual system across primates, nonhuman primate species reveal intriguing similarities in the perception of visual illusions with one another and humans. This dissertation explored visual illusions across the Order Primates, including human adults and children, chimpanzees, rhesus monkeys, and capuchin monkeys, with a focus on when, why and for whom geometric illusions emerge. Geometric illusions occur when a target’s perceived properties (e.g., size, shape, color) are impacted by an illusory context. Specifically, I focused on similarities and differences in perceptual mechanisms across primate species and on the role of attention in illusion emergence. I also assessed the translational impact of visual illusions on everyday decision-making (i.e., food-choice behavior). Overall, this research demonstrated that illusions are complex, and they emerged differently across species as a function of processing mode (i.e., global versus local processing) and attentional control. Further, not all illusions were perceived equally. External factors including illusory array design (i.e., the relationship between target and inducer stimuli) and testing paradigm directly impacted illusion perception. Response competition emerged if the illusory array was too heavily weighted towards inducing stimuli, such that the inducers were the more salient element within the array relative to the target stimulus. These methodological challenges proved to be especially true for local processors (e.g., monkeys) that first perceived the individual elements within an array prior to perceiving the global figure. The manner in which illusions are presented to pre- and non-verbal species can constrain or perhaps create a scaffold for illusory perception. Comparative research as in this dissertation provides a deeper understanding of how context influences perception and choice and will shed light on how we see and subsequently interact with our world

The Investigation of Prosocial Behavior in a Tool Task by Capuchin Monkeys (Cebus Apella)

Humans are exceptional in their willingness to and frequency with which they help one another. However, nonhuman primates also exhibit prosocial behavior. Recently, a number of laboratory studies examining prosociality among primates have yielded conflicting results. These contradictory findings may be due to a reliance on human interaction, tokens, or interactions in the direct context of food, a highly valued resource for animals. The current study examined prosocial behavior among capuchin monkeys (Cebus apella) in a tool task designed to address these issues by examining whether capuchins would transfer a necessary tool to a partner in different payoff conditions. Some capuchins’ behavior indicated that they understood the task, passing the tool when a partner and food were present. Notably, tool transfer in both tasks was overwhelmingly active rather than passive, which is unusual in the context of food; indicating active prosocial behavior is present amongst primates other than cooperative breeders

Comparative Cognition: Past, Present, and Future

Comparative cognition is the field of inquiry concerned with understanding the cognitive abilities and mechanisms that are evident in nonhuman species. Assessments of animal cognition have a long history, but in recent years there has been an explosion of new research topics, and a general broadening of the phylogenetic map of animal cognition. To review the past of comparative cognition, we describe the historical trends. In regards to the present state, we examine current “hot topics” in comparative cognition. Finally, we offer our unique and combined thoughts on the future of the field

Do Social Conditions Affect Capuchin Monkeys’ (Cebus apella) Choices in a Quantity Judgment Task?

Beran et al. (2012) reported that capuchin monkeys closely matched the performance of humans in a quantity judgment test in which information was incomplete but a judgment still had to be made. In each test session, subjects first made quantity judgments between two known options. Then, they made choices where only one option was visible. Both humans and capuchin monkeyswere guided by past outcomes, as they shifted from selecting a known option to selecting an unknown option at the point at which the known option went from being more than the average rate of return to less than the average rate of return from earlier choices in the test session. Here, we expanded this assessment of what guides quantity judgment choice behavior in the face of incomplete information to include manipulations to the unselected quantity.We manipulated the unchosen set in two ways: first, we showed the monkeys what they did not get (the unchosen set), anticipating that “losses” would weigh heavily on subsequent trials in which the same known quantity was presented. Second, we sometimes gave the unchosen set to another monkey, anticipating that this social manipulation might influence the risk-taking responses of the focal monkey when faced with incomplete information. However, neither manipulation caused difficulty for the monkeys who instead continued to use the rational strategy of choosing known sets when they were as large as or larger than the average rate of return in the session, and choosing the unknown (riskier) set when the known set was not sufficiently large. As in past experiments, this was true across a variety of daily ranges of quantities, indicating that monkeys were not using some absolute quantity as a threshold for selecting (or not) the known set, but instead continued to use the daily average rate of return to determine when to choose the known versus the unknown quantity

Differential Responding by Rhesus Monkeys (Macaca mulatta) and Humans (Homo sapiens) to Variable Outcomes in the Assurance Game

Behavioral flexibility in how one responds to variable partner play can be examined using economic coordination games in which subjects play against a variety of partners and therefore may need to alter their behavior to produce the highest payoff. But how do we study this behavioral flexibility once players have settled on a response? Here, we investigated how responding by rhesus monkeys (Macaca mulatta) and humans (Homo sapiens) playing a computerized single-player version of a coordination game, the Assurance game, changed as a function of the variable responses (Stag/Hare) generated by multiple simulations (SIMs). We were interested in whether individuals could track and differentially respond to changing frequencies of Stag and Hare play by the SIMs, especially with regard to the payoff dominant (Stag-Stag) outcome, something that could not be done with real partners as they quickly settled on the Stag response. For both monkeys and humans, there was a linear relationship between proportion of Stag play by the subject and the likelihood of the Stag choice by the SIM such that both species increased their use of Stag as the SIM increased its use of the Stag response. However, humans more closely matched their proportion of Stag responses to that of the SIM, whereas monkeys adopted a different, but equally effective, strategy of exploiting the higher-paying Stag alternative. These results suggest that monkeys and humans demonstrate sensitivity to a dynamic game environment in which they encounter variable contingencies for the same response options, although they may employ different strategies to maximize reward

How Is Chimpanzee Self-Control Influenced by Social Setting?

Self-control is often required in natural situations involving interactions with other individuals, and personal self-control can be compromised if other individuals act impulsively. In this study, we tested self-control in pairs of chimpanzees in a variety of settings where at least one chimpanzee of each pair performed an established test for self-control in which candies accumulated one at time as long as the chimpanzee did not eat any of them. When tested alone, some chimpanzees exhibited greater self-control as compared to when tested alongside a chimpanzee that independently performed the same type of test. However, when the nonfocal animal freely consumed rewards while the focal chimpanzee performed the accumulation task, the self-control of some focal chimpanzees was elevated as compared to when working alone. Finally, when the focal and nonfocal animals worked jointly on the same test and the number of rewards accumulated was dependent on both animals’ continued ability to inhibit eating the items, chimpanzees performed the same when housed together or in adjacent enclosures. On the whole, the effects of social setting were modest, but these results may relate to the literature on vicarious depletion of self-control, and they present interesting avenues for future research

Responses to the Assurance Game in Monkeys, Apes, and Humans Using Equivalent Procedures

There is great interest in the evolution of economic behavior. In typical studies, species are asked to play one of a series of economic games, derived from game theory, and their responses are compared. The advantage of this approach is the relative level of consistency and control that emerges from the games themselves; however, in the typical experiment, procedures and conditions differ widely, particularly between humans and other species. Thus, in the current study, we investigated how three primate species, capuchin monkeys, chimpanzees, and humans, played the Assurance (or Stag Hunt) game using procedures that were, to the best of our ability, the same across species, particularly with respect to training and pretesting. Our goal was to determine what, if any, differences existed in the ways in which these species made decisions in this game. We hypothesized differences along phylogenetic lines, which we found. However, the species were more similar than might be expected. In particular, humans who played using “nonhuman primate-friendly” rules did not behave as is typical. Thus, we find evidence for similarity in decision-making processes across the order Primates. These results indicate that such comparative studies are possible and, moreover, that in any comparison rating species’ relative abilities, extreme care must be taken in ensuring that one species does not have an advantage over the others due to methodological procedures

Tropospheric Ozone Assessment Report: assessment of global-scale model performance for global and regional ozone distributions, variability, and trends

The goal of the Tropospheric Ozone Assessment Report (TOAR) is to provide the research community with an up-to-date scientific assessment of tropospheric ozone, from the surface to the tropopause. While a suite of observations provides significant information on the spatial and temporal distribution of tropospheric ozone, observational gaps make it necessary to use global atmospheric chemistry models to synthesize our understanding of the processes and variables that control tropospheric ozone abundance and its variability. Models facilitate the interpretation of the observations and allow us to make projections of future tropospheric ozone and trace gas distributions for different anthropogenic or natural perturbations. This paper assesses the skill of current-generation global atmospheric chemistry models in simulating the observed present-day tropospheric ozone distribution, variability, and trends. Drawing upon the results of recent international multi-model intercomparisons and using a range of model evaluation techniques, we demonstrate that global chemistry models are broadly skillful in capturing the spatio-temporal variations of tropospheric ozone over the seasonal cycle, for extreme pollution episodes, and changes over interannual to decadal periods. However, models are consistently biased high in the northern hemisphere and biased low in the southern hemisphere, throughout the depth of the troposphere, and are unable to replicate particular metrics that define the longer term trends in tropospheric ozone as derived from some background sites. When the models compare unfavorably against observations, we discuss the potential causes of model biases and propose directions for future developments, including improved evaluations that may be able to better diagnose the root cause of the model-observation disparity. Overall, model results should be approached critically, including determining whether the model performance is acceptable for the problem being addressed, whether biases can be tolerated or corrected, whether the model is appropriately constituted, and whether there is a way to satisfactorily quantify the uncertainty

Association Between NRAS and BRAF Mutational Status and Melanoma-Specific Survival Among Patients With Higher-Risk Primary Melanoma

NRAS and BRAF mutations in melanoma inform current treatment paradigms but their role in survival from primary melanoma has not been established. Identification of patients at high risk of melanoma-related death based on their primary melanoma characteristics before evidence of recurrence could inform recommendations for patient follow-up and eligibility for adjuvant trials