Journal of Comparative Psychology

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)
A study of executive function in grey parrots (Psittacus erithacus): Experience can affect delay of gratification.
Executive function (EF) involves several abilities often correlated with success in various aspects of human life. Similar skills could also be advantageous to nonhumans, but few studies have effectively examined the extent of their EF abilities. Studies have also examined what experiences might strengthen/weaken human EF; might specific experiences also affect nonhuman EF? One type of EF often tested in both humans and nonhumans involves a delay of gratification—the ability to forgo an immediate reward to gain one either better in quality or quantity. We compared how Grey parrots (Psittacus erithacus) with somewhat different experimental histories performed when required to wait for more food—a difficult task for avian species. One laboratory-raised parrot, Griffin, had previously succeeded when asked to wait for a better reward and on other tasks purportedly involving some level of EF skills but failed to wait for a larger reward. After succeeding on a task designed to improve impulse control, he consistently waited for a larger reward, more nuts, for up to 15 min—far longer than most avian species tested. Two other parrots, Pepper and Franco, companion animals, had had no experience with delayed gratification tasks, but were as successful as Griffin on other EF-related studies in which they participated. These birds, with different histories than Griffin, also waited for more food for longer periods than most other birds, though not as consistently as Griffin. We suggest that specific types of experiences may strengthen EF in Grey parrots. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Impulsivity as a trait in domestic dogs (Canis familiaris): A systematic review and meta-analysis.
Impulsivity is a critical component of dog (Canis familiaris) behavior that owners often want to curtail. Though studies of dog impulsivity have examined their inability to wait and to inhibit inappropriate behaviors, it is not clear whether impulsivity is a behavioral trait with consistent characteristics across contexts. For this project, we conducted a systematic review and meta-analysis to investigate whether impulsivity exists as a behavioral trait in domestic dogs. Under a preregistered protocol, we processed over 10,000 bibliographic database records to uncover 13 articles with multiple impulsivity tasks assessed in the same subjects. Across 31 pairs of impulsivity tasks, 28 failed to detect a correlation in performance between tasks and three detected a correlation. For 15 correlations of impulsivity tasks with the owner’s perception of their dog’s impulsivity, 10 were not correlated, while five were correlated. A formal meta-analysis on one pair of tasks (A-not-B task and cylinder task) tested across seven different studies showed no overall correlation between the tasks. Our systematic review and meta-analysis found little indication of consistent relationships between impulsivity levels across tasks for dogs. Therefore, at the moment, we do not have good evidence of impulsivity as a behavioral trait that transfers across contexts, suggesting that perhaps we should focus on the context-specific nature of impulsivity in dogs. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Primate socio-ecology shapes the evolution of distinctive facial repertoires.
Primate facial musculature enables a wide variety of movements during bouts of communication, but how these movements contribute to signal construction and repertoire size is unclear. The facial mobility hypothesis suggests that morphological constraints shape the evolution of facial repertoires: species with higher facial mobility will produce larger and more complex repertoires. In contrast, the socio-ecological complexity hypothesis suggests that social needs shape the evolution of facial repertoires: as social complexity increases, so does communicative repertoire size. We tested these two hypotheses by comparing chimpanzees (Pan troglodytes) and gibbons (family Hylobatidae), two distantly related apes who vary in their facial mobility and social organization. While gibbons have higher facial mobility than chimpanzees, chimpanzees live in more complex social groups than gibbons. We compared the morphology and complexity of facial repertoires for both apes using Facial Action Coding Systems designed for chimpanzees and gibbons. Our comparisons were made at the level of individual muscle movements (action units [AUs]) and the level of muscle movement combinations (AU combinations). Our results show that the chimpanzee facial signaling repertoire was larger and more complex than gibbons, consistent with the socio-ecological complexity hypothesis. On average, chimpanzees produced AU combinations consisting of more morphologically distinct AUs than gibbons. Moreover, chimpanzees also produced more morphologically distinct AU combinations than gibbons, even when focusing exclusively on AUs present in both apes. Therefore, our results suggest that socio-ecological factors were more important than anatomical ones to the evolution of facial signaling repertoires in chimpanzees and gibbons. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Are chimpanzees futurists? Effects of motion lines and motion blur on the judgments of global motion direction in chimpanzees (Pan troglodytes).
Based on the invention and development of photography and movie in the 19th century, schools of contemporary art, such as Futurism, have emerged that express the dynamism of motion in painting. Painting techniques such as multiple stroboscopic images, motion blur, and motion lines are culturally based, but the biological basis of their perception has also been intensively investigated recently. Then what are the evolutionary origins of such pictorial representations of motion? Do nonhuman animals also have sensitivity to such representations? To address this question, we examined the effects of motion blur and motion lines on the judgments of global motion directions in chimpanzees. The results showed that the motion lines biased the chimpanzees’ judgments toward the direction of motion implied by them, whereas the effect of the motion blur was either absent or weak (Experiment 1). In Experiment 2, we manipulated the length and number of motion lines to examine the effect of “speed” and “distance” in addition to the motion direction implied by the motion lines. The results showed that the effect of motion lines became stronger as the length and the number of lines increased within a specific range. These results indicate that the motion lines also imply the direction of motion in chimpanzees and provide a clue to the evolutionary basis for the pictorial representations of motion. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Reach-to-grasp kinematic signatures in Colombian spider monkeys (Ateles fusciceps rufiventris).
A defining feature of most primates is a hand with five fingers. Spider monkeys are an exception because they have four fingers and no thumb. Despite the prevalence of reach-to-grasp research in primates, it is not known how the lack of a thumb affects reaching and grasping in spider monkeys. Drawing on patterns that have been well described in human adults, human infants, and other nonhuman primates, this study characterized prehension in Colombian spider monkeys (Ateles fusciceps rufiventris). Monkeys reached for two differently sized food objects and reaches were digitized offline for two-dimensional kinematic analysis. Grasp strategy was coded from video as preshaped when the hand was adjusted to grasp the food before contact, or not preshaped when the hand was adjusted to grasp the food after contact. Monkeys exhibited variability in reach smoothness that contrasted with the typical pattern seen in other adult primates and instead resembled the pattern observed in human infants. Monkeys anticipated the object to be grasped approximately half of the time. Reaches where the hand was preshaped to the object were smoother than reaches where the hand was adjusted to grasp after object contact. For the small object, reaches with preshaping were straighter than reaches without preshaping. Results are the first evidence of kinematic signatures for reach-to-grasp actions in spider monkeys. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Gaze in cats (Felis catus) and dogs (Canis lupus familiaris).
Within human–animal dyadic interactions, dog–human gaze has been identified as the crux of several important visual behaviors, such as looking back, gaze-following, and participation in an oxytocin feedback loop. It has been posited that this gaze behavior may have been motivated and sustained by cooperative relationships between dogs (Canis lupus familiaris) and humans (e.g., hunting, service roles), however, to investigate why gaze evolved, a comparison to a domesticated species that lacks a protracted history of cooperative companionship is needed: the domestic cat (Felis catus). In this study, we compare the gaze duration to owners of cats and dogs in a community science setting. We replicated previous gaze studies with dogs, wolves (Nagasawa et al., 2015), and dingoes (Johnston et al., 2017), requesting owners to sit with their pets for 5 min and interact as they normally would. Cats and dogs gazed at their owners for similar durations, but durations of petting and physical contact were significantly lower with cats. Gaze correlated significantly with vocalizations in dogs; however, no other correlations were significant. Dogs gazed less in our community science setting than dogs tested previously in-lab (Nagasawa et al., 2015). Ultimately, cats resemble dogs in their general gaze patterns, but not in most interactions with their owner. Future research should aim to include feral cats or wild cat species to shed light on gaze behavior development in the genus, while more community science work can identify the behaviors that shift for dogs between familiar and unfamiliar environments. (PsycInfo Database Record (c) 2024 APA, all rights reserved)

Journal of Comparative Psychology - Vol 138, Iss 1