No evidence of attentional bias toward threatening conspecific and allospecific faces in capuchin monkeys (Sapajus [Cebus] apella) using a dot-probe task.

The ability to quickly perceive and interpret threatening facial expressions from others is critical for successfully maintaining group cohesion in social nonhuman primate species. Rapid detection of threatening or negative stimuli in the environment compared to neutral stimuli, referred to as an attentional bias toward threat, is adaptive in that faster threat detection can lead to greater survival outcomes. However, the evolutionary roots of attentional bias formation toward social threat are not well understood. The present study investigated attentional biases toward social threat and the factors associated with them, including underlying hormonal mechanisms, in socially housed capuchin monkeys. Attentional biases were assessed using a dot-probe task that measured capuchins' latency to respond to a target using a joystick after viewing threatening or neutral conspecific or allospecific faces or nonface stimuli. In our first study, we examined how age, dominance status, sex, and cortisol level related to attentional biases. In our second study, we examined how manipulated oxytocin (OT) influenced attentional biases. Capuchin monkeys did not show attentional biases toward threatening faces or objects, but they showed attentional avoidance of scrambled familiar conspecific face stimuli. Cortisol and social rank were associated with attentional bias toward threat in the capuchin monkeys that participated in this study, which suggests that stress and dominance relate to attentional bias toward social threat. Manipulated OT increased attentional avoidance of scrambled familiar and unfamiliar face images, but not unscrambled faces or objects. Overall, we did not find compelling evidence of attentional biases toward social threat in capuchin monkeys. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Maze runners: monkeys show restricted Arabic numeral summation during computerized two-arm maze performance.

Mazes have been used in many forms to provide compelling results showcasing nonhuman animals' capacities for spatial navigation, planning, and numerical competence. The current study presented computerized two-arm mazes to four rhesus macaques. Using these mazes, we assessed whether the monkeys could maximize rewards by overcoming mild delays in gratification and sum the values of Arabic numerals. Across four test phases, monkeys used a joystick controller to choose one of two maze arms on the screen. Each maze arm contained zero, one or two Arabic numerals, and any numerals in the chosen maze arm provided the monkeys with rewards equivalent to the value of those numerals. When deciding which arm to enter, monkeys had to consider distance to numerals and numeral value. In some tests, gaining the maximum reward required summing the value of two numerals within a given arm. All four monkeys successfully maximized reward when comparing single numerals and when comparing arms that each contained two numerals. However, some biases occurred that were suboptimal: the largest single numeral and the delay of reward (by placing numerals farther into an arm from the start location) sometimes interfered with the monkeys' abilities to optimize. These results indicate that monkeys experience difficulties with inhibition toward single, high valence stimuli in tasks where those stimuli must be considered in relation to overall value when represented by symbolic stimuli such as numerals.

Editorial.

The Journal of Comparative Psychology (JCP) is the flagship APA journal dedicated to understanding psychological processes from a comparative perspective. Traditionally, "comparative" has meant comparison across species. However, "comparative" means more than just assessing as many species as possible or relating species to each other. I also think of the importance of a "comparative psychology" perspective in two other ways that should be reflected in the journal's publications. I would like to outline a few important points about how I view the mission of JCP, and how my term as chief editor will address some of the major issues that exist for the journal and for the field of comparative psychology more broadly. Preregistration, replication, and the review process are highlighted. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

On parrots, delay of gratification, executive function, and how sometimes we do the best we can.

Engaging executive functions provides an individual with the means to engage in cognitive control by adjusting to the environment and processing information in a way that leads to optimal outcomes. There are some claims that explicit training on certain executive functioning abilities provides benefits beyond the training tasks, but other studies indicate that this may not be true or may be limited based on age and other factors. This same mixed pattern has been reported with nonhuman species, where training or even experience in one specific area, like inhibition, sometimes leads to positive transfer in new but similar tasks that presumably also require executive functions. Pepperberg and Hartsfield (2024) sought to determine whether experience in previous tasks that required different executive functions impacted how well three African grey parrots: Griffin, Pepper, and Franco could perform in a new assessment of delayed gratification. Griffin showed a clear and consistent capacity to wait through a delay for a quantitatively better reward. This suggested that the previous experience with the tokens aided improvement in the quantitative delay of gratification task with food items as the options to choose between. The other two parrots, Pepper and Franco, never completed the intended sequence of phases in their study. Unfortunately, the testing conditions dictated by COVID restrictions were such that these two subjects appeared to exhibit stress in doing the task, and so no further testing was conducted with them. This article is an example of what can happen when two intelligent species (people and parrots) are put in difficult circumstances (a global pandemic unlike anything any of us has ever been through), and yet both species attempted to continue to engage in science. The effects of COVID-19 will remain an integral factor in comparative psychology for some time to come, and I suspect there are many other half-completed experiments that suffered because of the pandemic. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Chimpanzees (Pan troglodytes) with better task-based delay of gratification skills are rated as less impulsive, more agreeable, and smarter.

Delay of gratification and inhibitory control are generally considered measures of self-control. In humans, individual differences in measures of self-control are associated with a host of behavioral, neurological, cognitive, and health-related outcomes. Self-control is not unique to humans and has been demonstrated in a variety of nonhuman species using a variety of paradigms. In this study, the effect of sex and age on delay of gratification performance, as measured by the hybrid delay task, was tested in a sample of 88 chimpanzees. Additionally, whether individual differences in hybrid delay task performance were associated with different aspects of personality was examined in this study. Contrary to reports in human subjects, geriatric male chimpanzees were found to perform more efficiently than adult males, while no age differences were found between geriatric and adult females. Indeed, delay of gratification efficiency was positively associated with age in males and negatively associated with age in females. Chimpanzees that performed more efficiently on the hybrid delay task were also found to be rated as more intelligent, more extraverted, and less impulsive. These findings suggest that objective measures of efficiency in delay of gratification tasks are associated with different dimensions of personality, which have some overlapping construct validity. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Habitual prospective memory in preschool children.

Habitual prospective memory (PM) refers to situations in which individuals have to remember to perform a future task on a regular and frequent basis. Habitual PM tasks are ubiquitous and the ability to successfully complete these tasks (e.g., remembering to bring your lunch to school every day) is necessary for children as they begin to establish their own independence. The current investigation is the first to explore preschool children's ability to complete this kind of task. At the end of a regular testing session during which children engaged in a variety of unrelated cognitive tasks, participants were instructed to ask for a stamp on their card, which was sitting in a box on the table. Over the course of the first experiment, participants did this 13 times, spanning a time period of several months. The results demonstrated that children initially needed prompting from the experimenter to remember, but with experience, participants were able to retrieve this intention without assistance. Experiment 2 demonstrated that removing the box from participants' line of sight after numerous opportunities to perform the task did not negatively impact performance, although it did make a difference at the outset of this requirement to remember to ask for stamps. Together, these results indicate that with somewhat consistent and repeated practice, preschool children can fairly quickly demonstrate the ability to successfully perform future intentions that are likely to be repeated on numerous occasions.

Why do distractions sometimes aid self-control? Pigeons (Columba livia) highlight possible mechanisms underlying the distraction effect.

In this essay, the author explores the question of why distractions sometimes aid self-control. In a study with chimpanzees, Evans and Beran (2007) used two conditions with toys to address the possibility raised by Mueller et al. (2023) about toys as distractors. In the first, the accumulating rewards were within reach, and so chimpanzees had to inhibit taking rewards if more were to accumulate. The second condition was essential to this issue, as in that case toys also were available, but the delayed reward was out of reach (i.e., the chimpanzees were forced to wait to get the delayed reward). Because these trial types were intermixed, an explanation of the toys' effectiveness through conditioned association with the delayed reward would predict that the chimpanzees should have engaged the toys equally often in both conditions. However, three of four chimpanzees engaged the toys more when the accumulating reward was within reach compared to when it was not. Evans and Beran suggested that engagement with distractors in that study occurred when it was functionally effective in aiding delayed gratification, not solely as a result of toys being associated with delayed rewards, and thus was a cognitively controlled decision by the chimpanzees. The results of Evans and Beran (2007) have yet to be replicated in any other primate species. But, Mueller et al. (2023) noted that a study with a parrot (Koepke et al., 2015) showed that the parrot would use distractors and even move the smaller, sooner reward away from itself, perhaps matching the self-distraction techniques of children who hide their faces or talk to themselves. Thus, it remains to be determined whether those behaviors also can be explained by learned associations with reward or whether they reflect attention-based explanations. Mueller et al. (2023) have provided a creative experiment and a compelling argument that more careful analysis is needed of exactly what happens when an animal (or child) engages distractors and shows improved self-control, so that we can understand what role past reinforcement history may play and what possible attentional strategies or other cognitive strategies are at work in different self-control tasks. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Assessing aphantasia prevalence and the relation of self-reported imagery abilities and memory task performance.

Aphantasia is the experience of having little to no visual imagery. We assessed the prevalence rate of aphantasia in 5,010 people from the general population of adults in the United States through self-report and responses to two visual imagery scales. The self-reported prevalence rate of aphantasia was 8.9% in this sample. However, not all participants who reported themselves as aphantasic showed low-imagery profiles on the questionnaire scales, and scale prevalence was much lower (1.5%). Self-reported aphantasic individuals reported lower dream frequencies and self-talk and showed poorer memory performance compared to individuals who reported average and high mental imagery. Self-reported aphantasic individuals showed a greater preference for written instruction compared to video instruction for learning a hypothetical new task although there were differences for men and women in this regard. Categorizing aphantasia using a scale measure and relying on self-identification may provide a more consistent picture of who lacks visual imagery.

I am as fooled as you are, say some primates but only sometimes.

The evidence of "cognitive impenetrability" is a byproduct of the fact that minds often must react quickly to sensory stimulation, and they must attempt to make visual stimuli meaningful given what the perceiver knows of the world. Hanus et al. remind us that such immediate decisions may, in fact, help keep us alive, but at the possible cost of sometimes misaligning visual perception and physical reality. That said, not all people fall prey to all illusions, and many individuals may only fall prey to some illusions, but not others. A big question is why this happens. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Focality and prospective memory in preschool children.

We examined the influence of prospective memory (PM) cue focality in a sample of preschool children. Prior investigations in older populations indicated that focal targets were associated with enhanced PM performance, perhaps through more automatic retrieval processes. Importantly, this influential variable has not been thoroughly explored in younger samples. Over three test sessions, preschool children completed a memory task where they were shown a series of animals. During retrieval, participants were shown all of the animals except for one, and they had to name the missing animal. While engaged in this task, participants in the focal PM condition were instructed to remove particular animals (e.g., spider) from the game if they saw them. In the nonfocal condition, participants were told to remove any animal that was entirely one color (e.g., black) if they saw them during the game. The results demonstrated no difference in PM remembering between focal and nonfocal conditions. These results suggest that the effects of focality may not be present at the beginning stages of PM development. The implications for PM retrieval processes also are discussed.

Assessing the perception of face pareidolia in children (Homo sapiens), rhesus monkeys (Macaca mulatta), and capuchin monkeys (Sapajus apella).

Face pareidolia is the misperception of a face in an inanimate object and is a common feature of the face detection system in humans. Whereas there are many similarities in how humans and nonhuman animals such as monkeys perceive and respond to faces, it is still unclear whether other species also perceive certain nonface stimuli as faces. We presented a novel computerized task to capuchin monkeys (Sapajus apella), rhesus monkeys (Macaca mulatta), and preschool-aged children (Homo sapiens). This task trained subjects to choose faces over nonface images, and then presented pareidolia images with nonface images. All species selected faces most often on trials that included face images. However, only children selected pareidolia images at levels above chance. These results indicate that while children report perceiving face pareidolia, monkeys do not. These species differences could be due to human-unique experiences that result in an increased aptitude for anthropomorphizing objects with face-like patterns. It could also be due to monkeys showing a greater reliance on stimulus features rather than global, holistically organized cues that faces provide. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

I'll (not) take that: The reverse-reward contingency task as a test of self-control and inhibition.

While searching for more evidence of quantitative skills in chimpanzees to add to what she already had found, Boysen discovered something else. When training chimpanzees to point at what they would not get, and not pointing at what they would get, none could do this for piles of food items. Even when those items in the pointed-at set were given away to another chimpanzee, and even with experience in the task, failure persisted. This test, the reverse-reward contingency test, has now been used with many species, as a means of assessing inhibitory control and perhaps self-control in animals. Typically, the task is difficult, and only specific manipulations have worked to allow primates to overcome the reversed contingencies. This includes using symbolic stimuli, adding another layer to the story, and more value to the task itself as a measure perhaps of forms of cognitive control in other species. I will discuss some of these empirical results, including from other chimpanzees who were given variations of the task, and how these studies have influenced numerous areas within comparative cognitive science.

Congratulations to Animal Cognition on its 50th birthday! Some thoughts on the last 50 years of animal cognition research.

In this article, the author reflects on some of the key issues that have arisen in comparative cognition and the role and impact of the journal Animal Cognition through its first 25 years by pretending to look back at this period from the year 2047. Successes within comparative cognition are described and the role that Animal Cognition has played in the growth of comparative cognition are discussed. Concerns are presented about issues that affect the opportunities that researchers have to work with nonhuman species and to produce good comparative cognitive science. Prescriptions for what the author hopes will happen next also are offered all in the lens of a prospectively imagined retrospective on this field.

Children (Homo sapiens), but not rhesus monkeys (Macaca mulatta), perceive the one-is-more illusion.

Visual illusions are of particular interest to cognitive researchers because they reflect the active role of the brain in processing the world around us. Yousif and Scholl (2019) recently described a new visual experience, the one-is-more illusion, in which adult humans perceived continuous objects as longer than sets of discrete objects of equal length. In the current study, we investigated this phenomenon in human children (Homo sapiens) and rhesus macaques (Macaca mulatta). Children were presented with a computerized 2-choice discrimination task and successfully selected the longer of 2 images for control trials. On trials in which 2 versions of the same image were presented (identical in length), and one was of a continuous form and the other consisted of 2 or more distinct units, children showed a bias for the continuous object. Monkeys were given the same computerized task and learned to choose the longer of 2 otherwise identical stimuli. However, monkeys did not show a bias to choose the continuous probe images as longer than the discrete images in the critical test trials with equal-length stimuli. These results are discussed in light of developmental and comparative research on related illusory experiences and perceptual mechanisms. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Consistently Inconsistent Perceptual Illusions in Nonhuman Primates: The Importance of Individual Differences.

Perceptual illusions, and especially visual illusions, are of great interest not only to scientists, but to all people who experience them. From a scientific perspective, illusory visual experiences are informative about the nature of visual processes and the translation of sensory experiences to perceptual information that can then be used to guide behavior. It has been widely reported that some nonhuman species share these illusory experiences with humans. However, it is consistently the case that not all members of a species experience illusions in the same way. In fact, individual differences in susceptibility may be more typical than universal experiences of any given illusion. Focusing on research with the same nonhuman primates who were given a variety of perceptual illusion tasks, this "consistent inconsistency" is clearly evident. Additionally, this can even be true in assessments of human illusory experiences. Individual differences in susceptibility offer an important avenue for better understanding idiosyncratic aspects of visual perception, and the goal of isolating any possible universal principles of visual perception (in primates and beyond) should address these individual differences.

The evolution of quantitative sensitivity.

The ability to represent approximate quantities appears to be phylogenetically widespread, but the selective pressures and proximate mechanisms favouring this ability remain unknown. We analysed quantity discrimination data from 672 subjects across 33 bird and mammal species, using a novel Bayesian model that combined phylogenetic regression with a model of number psychophysics and random effect components. This allowed us to combine data from 49 studies and calculate the Weber fraction (a measure of quantity representation precision) for each species. We then examined which cognitive, socioecological and biological factors were related to variance in Weber fraction. We found contributions of phylogeny to quantity discrimination performance across taxa. Of the neural, socioecological and general cognitive factors we tested, cortical neuron density and domain-general cognition were the strongest predictors of Weber fraction, controlling for phylogeny. Our study is a new demonstration of evolutionary constraints on cognition, as well as of a relation between species-specific neuron density and a particular cognitive ability. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.

No evidence of the choice overload effect in a computerized paradigm with rhesus macaques (Macaca mulatta) and capuchin monkeys (Sapajus apella).

Given the choice, people are often drawn toward more options over fewer options in decision-making scenarios. However, mounting evidence indicates that sometimes, choosing from large arrays can result in suboptimal outcomes. The tendency to be overwhelmed, regretful, or less satisfied with a choice when there are many options to choose from is called choice overload. This effect has been well-studied in adult humans, but comparative research, such as with nonhuman primates, is lacking, despite the fact that such choice behavior may be related to general aspects of cognition that underlie behaviors such as foraging in the wild. In addition, research with monkeys can shed light on whether choice overload is a human-unique phenomenon that may be driven by sociocultural factors, or whether this effect may be shared more broadly among mammals. This experiment tested whether monkeys were susceptible to choice overload effects by using a computerized paradigm in which monkey subjects could choose from three, six, or nine task options. No evidence of choice overload was found for monkeys, although this may have been due to methodological limitations that are described.

Nonhuman primates learn adjacent dependencies but fail to learn nonadjacent dependencies in a statistical learning task with a salient cue.

There is ample evidence that humans and nonhuman animals can learn complex statistical regularities presented within various types of input. However, humans outperform their nonhuman primate counterparts when it comes to recognizing relationships that exist across one or several intervening stimuli (nonadjacent dependencies). This is especially true when the two elements in the dependency do not share any perceptual similarity (arbitrary associations). In the present study, we investigated whether manipulating the saliency of the predictive stimulus would enhance nonadjacent dependency learning in nonhuman primates. Rhesus macaques and tufted capuchins engaged in a computerized signal detection task that included sequences that were random in nature, included an adjacent dependency, or included a nonadjacent dependency. We manipulated the saliency of the predictive stimulus, such that the predictor jittered in place on the screen in some grammar blocks, as well as the transitional probability (the likelihood of the stimulus preceding the target to accurately predict the target's appearance) from block to block. Some monkeys evidenced learning of adjacent dependencies by faster response times to targets that followed a predictive stimulus compared to targets that were not preceded by a predictor. However, consistent with the body of evidence that indicates that nonhuman animals' statistical learning mechanisms are not at the same level of sophistication as humans', there was no evidence that monkeys learned nonadjacent dependencies of arbitrary associations, even when the salient cue was present.

Children and monkeys overestimate the size of high-contrast stimuli.

The letter height superiority effect reveals that human adults judge letters to be taller than identically sized pseudoletters. This effect extends to words, such that words are estimated to be greater in size or lasting longer in duration than pseudowords of the same size or those presented for the same duration. The physical properties of letters and words also impact their perceived size, such that higher contrast between figure-ground stimuli leads to greater size estimates. Specifically, black letters on a white background (high contrast between figure and ground) are judged to be taller than gray letters and gray pseudoletters on a white background (low contrast between figure and ground) for adult humans. In the current study, we assessed whether this effect would extend to nonverbal stimuli (shapes) such that high-contrast shapes would lead to greater size estimates relative to low-contrast shapes for human children and rhesus monkeys in a two-choice discrimination task. We found that children and monkeys tended to overestimate the size of high-contrast shapes relative to low-contrast shapes consistent with results reported among human adults. Implications for perceptual fluency and its impact on subjective size estimates are discussed.

A chimpanzee recognizes varied acoustical versions of sine-wave and noise-vocoded speech.

Previous research demonstrated that a language-trained chimpanzee recognized familiar English words in sine-wave and noise-vocoded forms (Heimbauer et al. Curr Biol 21:1210-1214, 2011). However, those results did not provide information regarding processing strategies of the specific acoustic cues to which the chimpanzee may have attended. The current experiments tested this chimpanzee and adult humans using sine-wave and noise-vocoded speech manipulated using specific sine-waves and a different number of noise bands, respectively. Similar to humans tested with the same stimuli, the chimpanzee was more successful identifying sine-wave speech when both SW1 and SW2 were present - the components that are modeled on formants F1 and F2 in the natural speech signal. Results with noise-vocoded speech revealed that the chimpanzee and humans performed best with stimuli that included four or five noise bands, as compared to those with three and two. Overall, amplitude and frequency modulation over time were important for identification of sine-wave and noise-vocoded speech, with further evidence that a nonhuman primate is capable of using top-down processes for speech perception when the signal is altered and incomplete.