Journal of Comparative Psychology

Are birds smarter than mathematicians? Pigeons (Columba livia) perform optimally on a version of the Monty Hall Dilemma.
The “Monty Hall Dilemma” (MHD) is a well known probability puzzle in which a player tries to guess which of three doors conceals a desirable prize. After an initial choice is made, one of the remaining doors is opened, revealing no prize. The player is then given the option of staying with their initial guess or switching to the other unopened door. Most people opt to stay with their initial guess, despite the fact that switching doubles the probability of winning. A series of experiments investigated whether pigeons (Columba livia), like most humans, would fail to maximize their expected winnings in a version of the MHD. Birds completed multiple trials of a standard MHD, with the three response keys in an operant chamber serving as the three doors and access to mixed grain as the prize. Across experiments, the probability of gaining reinforcement for switching and staying was manipulated, and birds adjusted their probability of switching and staying to approximate the optimal strategy. Replication of the procedure with human participants showed that humans failed to adopt optimal strategies, even with extensive training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
How orangutans (Pongo pygmaeus) innovate for water.
We report an observational field study that aimed to identify innovative processes in rehabilitant orangutans’ (Pongo pygmaeus) water innovations on Kaja Island, Central Kalimantan, Indonesia. We tested for the basic model of innovating (make small changes to old behavior), 4 contributors (apply old behavior to new ends, accidents, independent working out, social cross-fertilization), development, and social rank. Focal observations of Kaja rehabilitants’ behavior over 20 months yielded 18 probable innovations from among 44 water variants. We identified variants by function and behavioral grain, innovations by prevalence, and innovative processes by relations between innovations, other behaviors, and social encounters. Findings indicate innovating by small changes and some involvement of all 4 contributors; midrank orangutans were the most innovative; and rehabilitants’ adolescent age profile, orphaning, and intense sociality probably enhanced innovativeness. Important complexities include: orangutan innovating may favor certain behavioral levels and narrowly defined similarities, and it may constitute a phase-like process involving a succession of changes and contributors. Discussion focuses on links with great ape cognition and parallels with innovating in humans and other nonhuman species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Conditional copying fidelity in capuchin monkeys (Cebus apella).
In the last two decades, it became largely accepted that monkeys show little, if any, copying fidelity. However, some recent studies have begun to challenge this notion. To explore reasons for such contrary findings, we designed a foraging apparatus so that in each of two experiments with capuchin monkeys (Cebus apella), a model would demonstrate one of two alternative methods to obtain food. The apparatus had a V-shaped track on which a panel could be slid up left or right from the center to reveal food. In Experiment 1, food was located in a cup directly behind the center panel. In Experiment 2, sliding the panel left or right revealed food either in left or right ends of the V-track. Since this sliding movement led directly to one food location exclusive of the other, we predicted capuchins would show greater copying fidelity in this second Experiment. Instead, subjects were significantly more faithful to the model’s method in Experiment 1, which provided strong evidence of capuchins copying what they had observed. We suggest that the contrasting results of Experiment 1 may have occurred because capuchins prioritize exploratory behavior when alternative foraging locations are accessible. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Male-male and male-female aggression may influence mating associations in wild octopuses (Abdopus aculeatus).
Abdopus aculeatus engages in frequent aggression and copulation, exhibits male mate-choice, and employs multiple mating tactics. Here we draw upon established hypotheses to compare male–male aggression (MMA) and male–female aggression (MFA), as they relate to their mating behavior in the wild. When contesting for females, males appear to balance mate preference (resource value) with perceived chances of winning contests (resource holding potential). Although males spent more time mating with and contesting for large “Adjacent Guarded” females (those occupying a den within arm’s reach of a large “Adjacent Guarding” male), they exhibited higher rates of aggression over nonadjacent “Temporarily Guarded” females that may be more accessible. The major determinant of male-male aggressive success was size, and this factor may dictate the expression of conditional mating tactics in males. “Adjacent Guarding” males were the largest and most aggressively successful males, earning the most time copulating with females. They are considered to have the highest resource holding potential (RHP) in MMA. By contrast, in MFA, some larger individuals fled from smaller individuals, indicating that RHP appears to be a function of both size and sex in intersexual aggression. This result suggests variation in aggressiveness, or potential for severe injury—even sexual cannibalism during MFA. Male–female aggression may also be influenced by the sexual nonreceptivity of some individuals, or attempts by both sexes to increase foraging behavior by delaying mate-guarding activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Spatial memory in dogs (Canis familiaris) on a radial maze.
Working spatial memory in dogs (Canis familiaris) was tested in Experiments 1 and 2 on an 8-arm radial maze. When dogs chose freely among all 8 arms containing food in Experiment 1, they learned to enter all 8 arms with progressively fewer arm visits over trials. In Experiment 2, 2 groups of dogs were forced to visit 4 randomly chosen arms on the maze and then tested for memory of these arm visits using a win-shift rule for 1 group and a win-stay rule for the other group. Dogs performed better with the win-shift rule than with the win-stay rule. In Experiment 3, reference memory was investigated by using a 4-arm maze on which 0, 1, 3, and 6 pieces of food were consistently placed on different arms. Dogs learned to visit the arms with the larger amounts before the arms with the smaller amounts. Dogs’ memory capacity in these studies was found to be surprisingly low. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Evidence of human-like, holistic face processing in spider monkeys (Ateles geoffroyi).
Human subjects build mental representations of facial identity that are “holistic.” This has been clearly demonstrated with the composite effect where the representation of a whole face interferes with the recognition of features. Very few studies have sought evidence of holistic representations being built by nonhumans. This study tested captive, black-handed spider monkeys (N = 2) on a standard composite task, comparable to those run previously on human subjects. In Experiment 1, the monkeys were tested with the faces of conspecifics (Ateles geoffroyi), humans (Homo sapiens), and domestic sheep (Ovis aries) together with stick objects. The results of Experiment 1 revealed that both conspecific and human faces were processed holistically. The subsequent test (Experiment 2) confirmed that, for both subjects, the face composite effect was contingent on upright orientation. A direct comparison with available human data demonstrates a level of similarity, strongly suggestive of cognitive homology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
The development of sexual behavior in túngara frogs (Physalaemus pustulosus).
We examined the emergence of a critical component of sex, response to sexual signals—phonotaxis—in male and female túngara frogs (Physalaemus pustulosus). We determined the ontogenetic trajectories of phonotactic responses as animals developed from metamorphic froglets to reproductive adults. The results demonstrated that species-typical phonotaxis emerges quite early during postmetamorphic development, well before sexual maturity, suggesting that a developmentally early bias in the auditory system for species-typical signals might be a more general phenomenon than previously thought, and that the neural circuits responsible for processing and responding to conspecific advertisement signals in a species-typical manner might develop long before the coordinated behavior is demanded of the organism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Human perception of vocalizations of domestic piglets and modulation by experience with domestic pigs (Sus scrofa).
Interspecific communication between humans and pets is possible through vocal cues. We studied how humans with differing experience with domestic pigs (Sus scrofa) interpret pig vocalizations. Forty-eight ethologists studying pigs, 31 pig-caretakers and 54 naive students evaluated the emotional intensity and valence (negative/positive) of recordings from two negative (castration, isolation) and two positive (reunion with the sow, postsuckling) contexts. They also identified the context in which the recordings were made. Castration vocalizations were evaluated as highly intense and unpleasant. The positive contexts were evaluated as low in intensity and positive in valence, and isolation fell in the middle for both intensity and valence. Compared with the other two groups, pig-caretakers evaluated the intensity of vocalizations as lower, and ethologists evaluated the valence as more negative. The level of successful classification exceeded that expected by chance for all four contexts but was especially accurate for castration. Ethologists achieved better recognition than students. Classifying (right context) and understanding the emotional content (valence, intensity) of pig vocalizations is thus a general ability of humans, although it varies according to an individual’s experience with pigs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Are there species-universal categories in bird song phonology and syntax? A comparative study of chaffinches (Fringilla coelebs), zebra finches (Taenopygia guttata), and swamp sparrows (Melospiza georgiana).
Previous studies of learned bird song have suggested the existence of species-universal patterns in song organization: clear clusters in produced songs that do not vary within a species. Here the authors combine a computational method of comparing songs with statistical methods of assessing cluster structure to investigate this issue in a more quantitative manner. The authors first analyze song phonology and then examine song syntax at a population level in 3 species with very different song structure: chaffinches (Fringilla coelebs), zebra finches (Taenopygiaguttata), and swamp sparrows (Melospiza georgiana). The authors used a dynamic time-warping algorithm to compare song elements, which closely matched the judgments of human observers. Clustering tendency and validation statistics showed that broad phonological categories existed in all 3 species, but these categories explained no more than half of the overall phonological variation. The authors developed a novel statistic to assess syntactical structure, which indicated that element transitions were not randomly distributed. In the clearest case, in chaffinches, this could be explained by syllables being linked to certain positions within the song. These results demonstrate measures of song organization that can be applied across species, enhancing the potential of comparative studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
Mechanisms of call note-type perception in black-capped chickadees (Poecile atricapillus): Peak shift in a note-type continuum.
We report on operant conditioning and artificial neural network (ANN) simulations aimed at further elucidating mechanisms of black-capped chickadee chick-a-dee call note category perception. Specifically, we tested for differences in the speed of acquisition among different discrimination tasks and, in two selected discrimination groups, searched for evidence of peak shift. Earlier, unreported ANN data were instrumental in providing the motivation for the current set of studies with chickadees and are provided here. The ANNs revealed differences in the speed of learning among note-type discrimination groups that is related to the degree of perceptual similarity among the three note types tested (i.e., A, B, and C notes). In many respects, bird and network results were in agreement (i.e., in the observation of peak shift in the same group), but they also differed in important ways (i.e., all discrimination groups showed differences in speed of learning in simulations but not in chickadees). We suggest that the start, peak and end frequency of the chick-a portion of chick-a-dee call notes, which form a graded but overlapping continuum, may drive the peak shift observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)

Journal of Comparative Psychology - Vol 124, Iss 1