Adaptable navigation in bull ants (Myrmecia midas).

In an early scientific description of navigation (finding one's way from a known location to a known destination) in an arthropod, Charles Turner, one of comparative psychology's staunchest early proponents of studying individual variation. The field of comparative psychology has caught up with Charles Turner. In this essay, the author presents an overview of the results of previous studies which suggest that several species of ants use vision effectively to navigate in three dimensions, in daylight, and in darkness. Bull ants, a species that navigates in dim light, have large compound eyes containing receptors that are sensitive to ultraviolet (UV), blue, and green regions of the electromagnetic spectrum. Islam et al.'s findings illustrate a very general point about behavior that comparative psychologists do (and should continue to) take seriously, theoretically, and empirically. When we take the time to look closely, the behavior of individuals varies in biologically and psychologically important ways, no matter the size of their bodies or nervous systems. The adaptability of individuals arises from variation within the individual over time, manifest in this study as the adoption of novel routes as circumstances required. The adaptability of populations arises from variation across individuals, evident in this study in ants that learned to travel directly to the edge of the barrier and ants that learned to travel directly to the barrier, then make a right-angle turn to travel along it to an edge. The sources and consequences of behavioral variability, within and across individuals, and its manifestations across species, must remain core concerns for comparative psychology, as they were for Charles Turner more than 100 years ago. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Rules and metarules: Adult cotton-top tamarins (Saguinus oedipus) and 5-year-old children (Homo sapiens) can master both.

Developmental psychologists have noted a similar timeline of change for children's use of different perspectives about the same objects or events, as in the use of different labels for the same object, an aspect of language, and in understanding other's knowledge or beliefs, an aspect of social cognition as reviewed in the study by Neiworth et al. Comparative psychologists are interested to know what cognitive flexibility looks like in other species and how such variation relates to life history, ecology, and phylogeny. The general pattern of results to date indicates that monkeys can master both intra- and interdimensional shifts, but intradimensional shifts are learned far more quickly than interdimensional shifts (reviewed in the study by Neiworth et al, 2022). Neiworth et al. report that they have conducted exactly this kind of comparative study: They examined cognitive flexibility in adult cotton-top tamarins and human children in three age groups as they participated in a modified version of the Dimensional Change Card Sort (DCCS). Neiworth et al.'s study offers an example of careful consideration of one such possibility: that of using the experimenter's postural orientation to the cards as an inadvertent aid. Here the authors had the benefit of prior work showing that tamarins follow human-provided cues to make a spatially discriminated choice only if the experimenter's head, body, and eyes oriented to a particular location. Thus, in this study, the experimenter kept their head and body centered in the testing space between the two cards and looked at a point on the wall directly behind the midpoint of the testing tray. But the DCCS task, in abstract form, has potentially broader comparative value than to examine cognitive flexibility in primates alone. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

End the search quickly: Pigeons (Columba livia) and humans (Homo sapiens) share the same bias.

Comments on an article by W. T. Herbranson et al. (see record 2022-07304-001). The article by Herbranson et al. illustrates the care that must be taken, both in designing comparative research and in interpreting the findings, to understand how specific features of experimental design impact each species' choices. Herbranson et al. presented to pigeons a decision-making challenge known informally as "The Secretary Problem", a problem cast in the form of selecting a candidate for a job. The task is to make a single choice among a finite set of options when these options are presented in succession. The chooser must select a given option or pass on to the next without knowing what the remaining options are. Decisions are final-one either rejects an option when it appears or selects that option, ending the search. The authors trained pigeons to recognize the "reward value" of five different colors on keys that they could peck. Herbranson et al. subsequently replicated the study with humans, presenting humans with probabilistic outcomes (rather than the certain outcomes of varying value presented in earlier studies with humans). Their aim was to explore the consequences of altering reinforcement options on humans' choices, so as to understand more fully the ways in which pigeons and humans approach this problem. Herbranson et al.'s work is an example of the power of carefully constructed comparative behavioral experiments to expand the understanding of ourselves and other species in unexpected ways. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

African striped mice (Rhabdomys) mind the neighbors.

This feature essay discusses the African striped mice (Rhabdomys) and how closely related-species differ in behavior based on their environment. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

One hundred years of the Journal of Comparative Psychology.

The year 2021 marks the 100th year of publication of the Journal of Comparative Psychology by the American Psychological Association. To mark the centennial of the Journal of Comparative Psychology, a series of essays by diverse authors will appear in the four issues of Volume 135. Some of them concern the history of the journal, key figures in its history, and of the discipline; others concern the discipline's current status and its likely near future (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Comparative psychology's founding mother, Margaret Floy Washburn.

A scientific discipline grows through the insights and labors of individual scientists, honed by their discussions among colleagues and the mentoring they provide to the next generation of scientists. Margaret Floy Washburn, president of the American Psychological Association in 1921, the founding year of the Journal of Comparative Psychology, was a large presence during the early years of comparative psychology. She was a consummate scientist in all the abovementioned dimensions: insights, labors, communicating with her peers (including, a century later, readers of her voluminous writings), and mentoring. This essay provides an overview of her professional life and, more importantly, a synopsis of her major theoretical work, Movement and Mental Imagery, published in 1916. Her theoretical insights are remarkably relevant to contemporary developments in comparative psychology and related subdisciplines in psychology. She is an admirable founding mother for the discipline. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

A new look at universals and specificities in the songs of humpback whales.

In this issue's featured article, Mercado and Perazio (2021) describe songs of humpback whales using acoustic qualities, in part to determine the degree of similarity in songs across time and space that have not been revealed by information-theoretic analyses. They are particularly interested in evaluating alternative explanations of song variations in humpback whales. They argue that if humpback whales' songs "are . . . transmitted through acoustic contact followed by imitation" (p. 29) then (a) songs of populations not in acoustic contact should diverge, (b) songs of the same population should diverge increasingly over time, and (c) song forms separated by multiple decades either within or across populations should be dissimilar. Alternatively, acoustic similarities in song structure across populations and/or across decades in the same population would challenge the hypothesis that socially mediated learning is the primary driver of variation in the structure of humpback whales' songs over time. If that is the case, then identifying universal properties of song composition is important to move the field forward. Broadening the analytical tool kit can help in this effort. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Odds favor the bees.

Muszynski and Couvillon (see record 2020-37265-001) built upon their previous findings that honeybees can learn the relation among triads of trial-unique visual stimuli. In this new work, they showed that bees encountering trial-unique sets of three or four visual stimuli chose the correct stimulus at above-chance levels, replicating their previous findings and extending them to four-choice displays. In the first experiment, the bees' performance with triads of stimuli was unaffected by whether the correct choice was patterned or solid, or whether the stimuli shared a common color. A control group in this experiment encountered a categorical discrimination problem with two stimuli. This latter group of bees easily learned the discrimination and made a lower proportion of errors than bees solving the oddity problem, suggesting that the bees did not perceive the oddity task as a discrimination problem. The possibility that bees solved the oddity problem as a categorical discrimination was further examined in a second experiment. In that experiment, one group of bees encountered quartets of disks in combinations of solid color and two-color disks, and another group encountered only two-color disks. The authors expected that the addition of an irrelevant category (solid or two-color disk) would make the odd stimulus more discriminable, and, therefore, improve performance in that group compared with the group that encountered only two-colored disks. Their expectation was confirmed: Bees that encountered stimuli with a categorical difference, even though the category was irrelevant to which disk (of four) was odd, averaged more correct choices (average .67 vs. .47 across 15 trials; .25 expected by chance) and reached a higher terminal level of performance than bees that encountered only two-color disks (nearing .90 vs. around .50 correct, Trials 14 -16, solid and pattern group vs. pattern-only group, respectively). (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Rats (Rattus norvegicus), like humans (Homo sapiens), detect auditory jitter.

One logical place to start in a wider search is to look for perception of auditory rhythm in diverse species. Celma-Miralles and Toro (see record 2019-59892-001), in this issue's Featured Article, report such a study. They tested whether rats and humans could detect deviations from one component of auditory rhythm, isochrony (a constant interval between sounds; Ravignani & Madison, 2017). Rats learned to poke their noses through an aperture, and humans learned to tap the spacebar on a keyboard, following an isochronous series of tones, and to refrain from these actions following an anisochronous series of tones (a Go/No go paradigm; Figure 1). In the anisochronic series of tones, the authors described the stimuli as having auditory jitter. Subsequently, the participants were presented with a mixture of familiar sound sequences and novel isochronous and anisochronous sound sequences at new tempi and with new absolute durations. Humans responded more than twice as frequently and rats just over 5% more frequently to the novel isochronous sound sequences than to the novel anisochronous sound sequences. Thus, both species provide evidence of discriminating jittery sounds from rhythmic sounds, and humans were more accurate at this task than rats. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Is the SNARC a boojum?

In this essay, the author notes that for the past half-century, psychologists have examined how humans make use of spatial representations when making judgments about numerical properties of sets of items. This line of work was initiated by Frank Restle (1970), who asked college students at Indiana University to choose the larger number, either the sum of A + B or C, as rapidly as possible. Restle found that the timing of people's choices fit an analog model of numerical judgment that had been proposed a few years earlier (Moyer & Landauer, 1967) and that people seemed to judge the magnitude of numbers by their position on a mental number line. The hypothetical number line is now called the "mental number line," and the effect on latency to respond to questions about numbers that results from use of the mental number line has been labeled the "Spatial Numerical Association of Response Codes" or SNARC for short. The author notes that she has parodied Frank Beach's (1950) title for his classic essay about the state of comparative psychology at the mid-20th century for the title of this piece. Beach, in turn, was inspired by Lewis Carroll's nonsense poem, " The Hunting of the Snark," published in 1876. The poem chronicles "the impossible voyage of an improbable crew to find an inconceivable creature," the snark. According to the poem, most species of snarks are relatively harmless. The boojum, however, is a dangerous snark, because those who catch sight of a boojum "suddenly vanish away." Here, the author wants to turn the meaning of the homonym SNARC a bit to suggest that the SNARC might itself vanish, perhaps to metamorphose into a more complex entity. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Dogs (Canis familiaris) ignore gravity.

Tecwyn and Buchsbaum (2018) in this issue challenge the idea that dogs display a persistent gravity bias. In four experiments, they probed where dogs search for a ball after it is dropped into a tube. First, they replicated diagonal tube task experiments previously conducted with apes (Cacchione & Call, 2010) to investigate how auditory and visual information about the tubes influenced the dogs' search. Next, they examined how dogs' search shifted when the middle location was no longer an option. Third, they probed whether dogs' search could be explained by proximity between the reward's release point and the search locations (a condition depicted in Figure 1). Finally, they presented tasks in which any of the biases that might have guided them in the previous experiments (namely, gravity, middle position, or proximity to the point where the ball was dropped) could not guide their search. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Bearded capuchin monkeys use joint synergies to stabilize the hammer trajectory while cracking nuts in bipedal stance.

The transition from occasional to obligate bipedalism is a milestone in human evolution. However, because the fossil record is fragmentary and reconstructing behaviour from fossils is difficult, changes in the motor control strategies that accompanied this transition remain unknown. Quadrupedal primates that adopt a bipedal stance while using percussive tools provide a unique reference point to clarify one aspect of this transition, which is maintaining bipedal stance while handling massive objects. We found that while cracking nuts using massive stone hammers, wild bearded capuchin monkeys (Sapajus libidinosus) produce hammer trajectories with highly repeatable spatial profiles. Using an uncontrolled manifold analysis, we show that the monkeys used strong joint synergies to stabilize the hammer trajectory while lifting and lowering heavy hammers. The monkeys stringently controlled the motion of the foot. They controlled the motion of the lower arm and hand rather loosely, showing a greater variability across strikes. Overall, our findings indicate that while standing bipedally to lift and lower massive hammers, an arboreal quadrupedal primate must control motion in the joints of the lower body more stringently than motion in the joints of the upper body. Similar changes in the structure of motor variability required to accomplish this goal could have accompanied the evolutionary transition from occasional to obligate bipedalism in ancestral hominins.

Persistent pigeons (Columba livia) learn how to produce a list.

In the Featured Article for this issue of the Journal of Comparative Psychology, Scarf, Johnston, and Colombo (2018) showed that pigeons learned to reproduce (by pecking icons presented on a screen) a four-item serially ordered list without specific training on that list, as macaques did (Figure 1). In Scarf et al.'s (2018) study, all five birds given structured training subsequently mastered multiple sets of two-item, then three-item, and finally four-item lists, with a diminishing training regime for the later four-item lists. Scarf et al.'s (2018) findings have at least two important implications for our science: First, members of evolutionarily distant taxa, pigeons and monkeys, can both produce a serially ordered set of four actions. Second, we are reminded that learning sets can be acquired for diverse tasks-the principles of learning set formation are very general. (PsycINFO Database Record

Editorial.

This editorial serves as an introduction for the new editorial team of the Journal of Comparative Psychology which is shifting from Chief Editor Josep Call and Associate Editor Irene Pepperberg to Chief Editor Dorothy Munkenbeck Fragaszy and Associate Editor Todd Freeberg. (PsycINFO Database Record

A new look at play fighting.

With this issue, the editors inaugurate the Featured Article Essay in the Journalof Comparative Psychology. This brief essay, written by one or both of the editors, highlights one of the articles in each issue that is found to be particularly important, interesting, or innovative. The editors' choice for this issue is the article by Pellis and Pellis (2018) about play fighting in gray mouse lemurs (Microcebus murinus). (PsycINFO Database Record

Unique perceptuomotor control of stone hammers in wild monkeys.

We analysed the patterns of coordination of striking movement and perceptuomotor control of stone hammers in wild bearded capuchin monkeys, Sapajus libidinosus as they cracked open palm nut using hammers of different mass, a habitual behaviour in our study population. We aimed to determine why these monkeys cannot produce conchoidally fractured flakes as do contemporary human knappers or as did prehistoric hominin knappers. We found that the monkeys altered their patterns of coordination of movement to accommodate changes in hammer mass. By altering their patterns of coordination, the monkeys kept the strike's amplitude and the hammer's velocity at impact constant with respect to hammer mass. In doing so, the hammer's kinetic energy at impact-which determines the propagation of a fracture/crack in a nut-varied across hammers of different mass. The monkeys did not control the hammer's kinetic energy at impact, the key parameter a perceiver-actor should control while knapping stones. These findings support the hypothesis that the perceptuomotor control of stone hammers in wild bearded capuchin monkeys is inadequate to produce conchoidally fractured flakes by knapping stones, as do humans.

"Vision for Action" in Young Children Aligning Multi-Featured Objects: Development and Comparison with Nonhuman Primates.

Effective vision for action and effective management of concurrent spatial relations underlie skillful manipulation of objects, including hand tools, in humans. Children's performance in object insertion tasks (fitting tasks) provides one index of the striking changes in the development of vision for action in early life. Fitting tasks also tap children's ability to work with more than one feature of an object concurrently. We examine young children's performance on fitting tasks in two and three dimensions and compare their performance with the previously reported performance of adult individuals of two species of nonhuman primates on similar tasks. Two, three, and four year-old children routinely aligned a bar-shaped stick and a cross-shaped stick but had difficulty aligning a tomahawk-shaped stick to a matching cut-out. Two year-olds were especially challenged by the tomahawk. Three and four year-olds occasionally held the stick several inches above the surface, comparing the stick to the surface visually, while trying to align it. The findings suggest asynchronous development in the ability to use vision to achieve alignment and to work with two and three spatial features concurrently. Using vision to align objects precisely to other objects and managing more than one spatial relation between an object and a surface are already more elaborated in two year-old humans than in other primates. The human advantage in using hand tools derives in part from this fundamental difference in the relation between vision and action between humans and other primates.

Variation among juvenile capuchins in social influences on exploration.

The exploratory or feeding activities of others might influence the timing, the place, or both, of exploratory activities among young group-living individuals, and this influence might affect the information gained by individuals during exploration. This study examined the temporal and spatial aspects of adults' influence on the exploratory behavior of juvenile capuchins, and on the juveniles' acquisition of a novel behavior. Two experimental apparatus, which were initially novel to the juvenile subjects but familiar to the adults, and which provided food when a tool was used properly, were presented to group-housed capuchin monkeys. The apparatus were presented (a) in a central area, in which all animals could interact with the apparatus and in which several older group members regularly solved the tasks (group site), and (b) in a protected site within the home cage (crèche) that only juveniles could enter, but from which the rest of the cage, including the group site, could be viewed. Juveniles contacted the apparatus at the crèche more often when there was no apparatus at the group site, but only half the individuals made greater use of the apparatus at the group site than at the crèche when an apparatus was present at both sites. Seven of nine used an apparatus more often when adults also had an apparatus, than when adults did not have an apparatus. These results indicate that juveniles' exploratory activity is only weakly related to adults' activity. The linkage appears closer for younger juveniles (20 months or less) than for older juveniles. Moreover, as only older juveniles learned to solve the tasks, coordination of exploration with adults was evidently not related to learning a new skill. © Wiley-Liss, Inc.

Prehension in Cebus and Saimiri: I. Grip type and hand preference.

Prehension was examined in tufted capuchins (Cebus apella) and squirrel monkeys (Saimiri sciureus). Individual subjects were videotaped from frontal and sagittal planes while they grasped small objects presented in several ways (in view, out of view, embedded, moving). Capuchins used a precision grip in 30% of trials and in more than half of trials with stationary objects. Most (54%) of the precision grips used were opposition of the thumb to the index finger; however, eight other forms were also observed. Squirrel monkeys never used a precision grip. Data on hand preference, preliminary data on movement velocity, and preliminary observations of movement trajectories (up to the time of hand shaping prior to contact with the object) do not indicate significant differences across genera in these aspects of prehension. The presence of varied precision grips in capuchins and no form of precision grip in squirrel monkeys leads to two conclusions. First, a thumb classification of "opposable" (vs. "pseudo-opposable") is not essential for precision gripping. Capuchins, with pseudo-opposable thumbs, use precision grips routinely. Second, the fundamental difference between these genera, which accommodates precision gripping in capuchins, is the capacity in capuchins (but not in squirrel monkeys) to produce lateral pressure between opposing digits. The anatomy of the spinal pyramidal tract and neuromuscular interfacing in the hands may be more sensitive gauges of manual dexterity than the anatomy of the thumb.