Showing papers in "Journal of Comparative Psychology in 1996"

Imitative learning of artificial fruit processing in children (Homo sapiens) and chimpanzees (Pan troglodytes)

Abstract: Observational learning in chimpanzees and young children was investigated using an artificial fruit designed as an analog of natural foraging problems faced by primates. Each of 3 principal components could be removed in 2 alternative ways, demonstration of only one of which was watched by each subject. This permitted subsequent imitation by subjects to be distinguished from stimulus enhancement. Children aged 2–4 years evidenced imitation for 2 components, but also achieved demonstrated outcomes through their own techniques. Chimpanzees relied even more on their own techniques, but they did imitate elements of 1 component of the task. To our knowledge, this is the first experimental evidence of chimpanzee imitation in a functional task designed to simulate foraging behavior hypothesized to be transmitted culturally in the wild.

Indexical and Referential Pointing in Chimpanzees (Pan troglodytes)

Abstract: The spontaneous index finger and other referential pointing in 3 adult, laboratory chimpanzees (Pan troglodytes) who have not received language training is reported. Of 256 total observed points, 254 were emitted in the presence of a human to objects in the environment; therefore, the points were communicative. Indicators of intentional communication used by the subjects included attention-getting behaviors, gaze alternation, and persistence until reward. Thus, pointing by these chimpanzees was intentionally communicative. These data imply that perspective-taking and referential communication are generalized hominoid traits, given appropriate eliciting contexts. Index finger pointing was more frequent with the subjects' dominant hands. This study refutes claims that indexical or referential pointing is species-unique to humans or dependent on linguistic competence or explicit training.

Behavioral and glucocorticoid responses of adult domestic dogs (Canis familiaris) to companionship and social separation

Abstract: Removal of 1 member of a long-standing pair of adult domestic dog (Canis familiaris) kennel mates from the home run for 4 hr had no effect on the behavior or plasma glucocorticoid levels of the remaining dog. When tested in a novel environment, dogs showed increased activity and elevated glucocorticoid levels at the end of the session, but these responses were as large when the dogs were with their kennel mates as when they were alone. However, activity and glucocorticoid levels were not elevated if the dogs were exposed to the novel environment in the presence of their human caretaker. Dogs more often were observed in proximity with, and soliciting social behavior from, the human than the kennel mate. These results highlight the importance of human companionship for the domestic dog and point to a difference in the nature of the social relationships of dogs with humans and with conspecifics.

Imitative learning in male Japanese quail (Coturnix japonica) using the two-action method.

Abstract: The study of imitative learning in animals has suffered from the presence of a number of confounding motivational and attentional factors (e.g., social facilitation and stimulus enhancement). The two-action method avoids these problems by exposing observers to demonstrators performing a response (e.g., operating a treadle) using 1 of 2 distinctive topographies (e.g., by pecking or by stepping). Japanese quail (Coturnix japonica) observers exposed to conspecific demonstrators showed a high correlation between the topography of the response they observed and the response they performed. These data provide strong evidence for the existence of true imitative learning in an active, precocious bird under conditions that control for alternative accounts.

Learning the configuration of a landmark array: I. Touch-screen studies with pigeons and humans.

Abstract: Pigeons and humans searched on a touch-screen monitor for an unmarked goal located relative to an array of landmarks presented in varied screen locations. After training with the goal centered in various square arrays of 4 landmarks, humans, but not pigeons, transferred accurately to arrays with novel elements. Humans searched in the middle of expanded arrays, whereas pigeons preserved the distance and direction to a single landmark. When trained with the goal centered below 2 identical horizontally aligned landmarks, humans responded to horizontal expansions or contractions of the array by shifting their search vertically, preserving angles from landmarks to goal. Pigeons did not adjust their search vertically. Humans trained with a single landmark adjusted search distance when landmark size was changed. Both pigeons and humans use the configuration of a landmark array, but the underlying processes seem to differ.

Hand preference for a bimanual task in tufted capuchins (Cebus apella) and rhesus macaques (Macaca mulatta).

Abstract: This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) and 55 rhesus macaque (Macaca mulatta) monkeys. Investigators presented subjects with plastic tubes lined with food and noted which hand the animals used to hold the tubes and which hand the animals used to remove the food. Several significant findings emerged from this investigation. First, rhesus macaques, but not tufted capuchins, exhibited a population-level bias toward use of the right hand (although the difference in direction of hand preference between species was not significant). Second, capuchins exhibited greater hand preference strength than did macaques. Third, among capuchins, but not among macaques, hand preference strength was greater for adults than for immatures. Finally, both species used their index digit to remove food most frequently when compared with other digits. Findings of hand preference direction and strength in this study were compared with other findings noted for chimpanzees which performed a bimanual tube task in a previous study. The authors conclude that using the same procedure to compare hand preference across species represents a powerful research tool that can lead to a more complete understanding of the evolution and ontogenesis of primate handedness.

Factors influencing young chimpanzees' (Pan troglodytes) recognition of attention.

Abstract: By 2 1/2 years of age, human infants appear to understand how others are connected to the external world through the mental state of attention and also appear to understand the specific role that the eyes play in deploying this attention. Previous research with chimpanzees suggests that, although they track the gaze of others, they may simultaneously be unaware of the underlying state of attention behind gaze. In a series of 3 experiments, the investigators systematically explored how the presence of eyes, direct eye contact, and head orientation and movement affected young chimpanzees' choice of 2 experimenters from whom to request food. The results indicate that young chimpanzees may be selectively attached to other organisms making direct eye contact with them or engaged in postures or movements that indicate attention, even though they may not appreciate the underlying mentalistic significance of these behaviors.

Early experience and plasticity of song in adult male zebra finches (Taeniopygia guttata)

Abstract: Zebra finches (Taeniopygia guttata) learn song primarily at 35-65 days of age, but birds deprived of experience at that stage may modify their songs later. Experiments on 5 groups examined the effect of varying early social experience on the plasticity of adult song. Major changes of song in adulthood were rare, and new syllables were memorized only in the more socially impoverished groups. Most songs underwent minor changes, in syllable structure or stereotypy, as well as in the addition or deletion of syllables. Two factors appeared to be important in determining the amount of change: the extent of social deprivation that the bird had experienced and, in the case of group-reared birds, the degree of song matching between social companions.

Odor preferences of female house mice (Mus domesticus) in seminatural enclosures.

Abstract: Preferences for male odors by female house mice (Mus domesticus) were examined with respect to age, dominance status, and spatial relationships. Mice were free living in 6 field enclosures. Estrous or nonestrous females were placed in an aquarium with soiled bedding from live traps as the odor source. Females were tested for preferences between (a) adult and juvenile male odors, (b) dominant and subordinate male odors, and (c) "near" and "far" male odors. In dominance odor tests, estrous females preferred odors from dominant males; nonestrous females exhibited no significant preferences. In adult-juvenile and spatial odor tests, there were no significant differences between odor preferences of estrous and nonestrous females. However, most females preferred odors from adult and "near" males. Male dominance status appears to be the strongest influence on female odor preference in these seminatural enclosures.

Effects of paced mating and intromissive stimulation on feminine sexual behavior and estrus termination in the cycling rat.

Abstract: The effects of differential mating stimulation on sexual behavior and estrus length were examined in cycling rats that could or could not self-regulate, or pace, the timing of sexual contact. Female rats (Rattus norvegicus) received 30 paced, 30 nonpaced, or 15 nonpaced followed by 15 paced intromissions during mating tests. Decreases in sexual responsiveness were seen during the second half of testing; pacing was associated with greater inter-intromission intervals, decreased proceptivity, and increased rejection behavior at this time. Female rats pacing during the second test half behaved similarly, regardless of prior treatment, showing that the number rather than the timing of prior intromissions affected subsequent behavior. However, estrus length was decreased by prior paced mating. These data suggest that changes in sexual responsivity occur throughout estrus and that the nature of these changes is differentially dependent on the type of mating stimulation received.

Kinship and familiarity as factors affecting social transfer of food preferences in adult Mongolian gerbils (Meriones unguiculatus).

Abstract: Experiments were carried out with Mongolian gerbils (Meriones unguiculatus) to assess whether a socially mediated acquisition of diet selection exists in this species. Results showed that a gerbil was influenced in its diet choices by information extracted during a brief period of interaction with a familiar conspecific that had recently eaten a novel food. Data revealed that the acquisition of a food preference from a conspecific depends on the existence of a social bond between the interacting gerbils. Either genetic relatedness (being brother or sister raised in different litters) or familiarity (being bred in the same litter or being member of a reproductive pair) is necessary for the transfer of information. Unfamiliar and unrelated observer gerbils did not selectively choose their demonstrator's food.

Grunt communication in human infants (Homo sapiens).

Abstract: Laryngeally produced vocalizations termed grunts function communicatively in many species. The vocalizations and accompanying behavior of 5 human infants videorecorded monthly at the transition to speech were analyzed to determine the frequency, physiological basis, and functional status of grunt production, a phenomenon systematically studied for the first time here. Earliest grunts occurred accompanying movement or effort; next, they accompanied acts of focal attention; and finally they were used in communication. Communicative use was followed by the onset of referential ability in language. This sequence is interpreted in relation to the physiological basis of these vocalizations in respiratory function and to additional developmental variables observed in the children. The findings have implications for the transition to the communicative repertoire in other species in which laryngeal function contributes to communication.

Macaque social culture: development and perpetuation of affiliative networks.

Abstract: Maternal affiliative relations may be transmitted to offspring, similar to the way in which maternal rank determines offspring rank. The development of 23 captive female rhesus monkeys (Macaca mulatta) was followed from the day of birth until adulthood. A multivariate analysis compared relations among age peers with affiliative relations, kinship, and rank distance among mothers. Maternal relations were an excellent predictor of affiliative relations among daughters, explaining up to 64% of the variance. Much of this predictability was due to the effect of kinship. However, after this variable had been controlled, significant predictability persisted. For relations of female subjects with male peers, on the other hand, maternal relations had no significant predictive value beyond the effect of kinship. One possible explanation of these results is that young rhesus females copy maternal social preferences through a process of cultural learning.

Postural asymmetries and language lateralization in humans (Homo sapiens).

Abstract: Is hemispheric specialization for speech more closely related to left hemisphere specialization for manual skill and sequencing, as is usually supposed, or to control of asymmetries in whole body posture, as recent findings of right-handedness in nonhuman primates suggest? This question can be evaluated in the 10% of humans who have mixed handedness and footedness. Footedness entails postural asymmetry, and persons with mixed limb preferences often prefer the hand ipsilateral to the preferred foot in asymmetrical actions for which whole body postural adjustments are obligatory (e.g., throwing). The dichotic listening test , and indicator of language laterality, was administered to 4 groups of 48 persons with the 4 possible combinations of hand and foot preference. As in 2 past studies, language lateralization was somewhat more strongly related to postural asymmetries than to asymmetries in manual skill and sequencing.

Mode of foraging competition is related to tutor preference in Zenaida aurita.

Abstract: This study compared the direction of social learning in 2 populations of Barbados Zenaida doves (Zenaida aurita). One population (St. James) is territorial; it competes aggressively with conspecifics but scramble competes with heterospecifics. The other population (Deep Water Harbour) forages in large homospecific flocks. Field observations were conducted to quantify intraspecific and interspecific patterns of foraging association and aggression. Wild-caught doves from both areas were then tested on novel foraging tasks demonstrated by either a conspecific or a heterospecific tutor. In all experiments, St. James doves learned more readily from the heterospecific tutor (Carib grackle -Quiscalus lugubris-), whereas Deep Water Harbour doves learned more readily from the conspecific tutor. The type of competitive feeding interaction in the field (i.e., scramble vs. interference) appears to better predict the pattern of social learning in an experiment than does species identity.

Concurrent absolute and relative pitch processing by European starlings (Sturnus vulgaris).

Abstract: In responding to sounds, birds use both relative and absolute pitch perception. As a means of testing which type of pitch perception is dominant, European starlings (Sturnus vulgaris) were trained to discriminate between low-ascending and high-descending sequences of tones. They were then tested with high-ascending and low-descending sequences during probe and transfer sessions. The birds could transfer their discrimination on the basis of either high versus low (absolute pitch) or ascending versus descending (relative pitch). During probe sessions, birds responded to nonreinforced novel sequences on the basis of absolute pitch. However, during transfer sessions, the birds could quickly learn to respond to reinforced novel sequences on the basis of relative pitch. The results indicate that during initial training, the birds learned about both relative and absolute aspects of the stimuli.

Hiding and perspective taking in long-tailed macaques (Macaca fascicularis)

Abstract: Seven long-tailed macaques (Macaca fascicularis) were trained by threats not to drink from a juice nipple as long as an experimenter was facing them. However, they were allowed to drink when the experimenter was standing with his or her back turned. During transfer tests, the monkeys had a choice between 2 juice nipples, one uncovered and the other hidden from the experimenter by a wooden screen, while the experimenter was facing them. We tested whether the monkeys would then prefer to drink behind the screen, thus demonstrating that they transferred knowledge acquired during training. Results did not yield a significant outcome, suggesting that the macaques did not transfer the observable "experimenter's visible open eyes" and that they did not take the experimenter's perspective.

Can Monkeys (Macaca mulatta) Represent Invisible Displacement

Abstract: Four experiments were conducted to assess whether or not rhesus macaques (Macaca mulatta) could represent the unperceived movements of a stimulus. Subjects were tested on 2 computerized tasks, HOLE (monkeys) and LASER (humans and monkeys), in which subjects needed to chase or shoot at, respectively, a moving target that either remained visible or became invisible for a portion of its path of movement. Response patterns were analyzed and compared between target-visible and target-invisible conditions. Results of Experiments 1, 2, and 3 demonstrated that the monkeys are capable of extrapolating movement. That this extrapolation involved internal representation of the target's invisible movement was suggested but not confirmed. Experiment 4, however, demonstrated that the monkeys are capable of representing the invisible displacements of a stimulus.

Effect of avian–human joint attention in allospecific vocal learning by grey parrots (Psittacus erithacus).

Abstract: The authors studied whether grey parrots (Psittacus erithacus) would learn referential English vocalizations if training lacked full social interaction with humans. In previous studies, grey parrots learned human vocalizations most readily when training simultaneously demonstrated the meaning (full reference) and function (full contextual applicability) of the utterance and actively engaged the subject in learning (full interaction). Those studies, however, did not contrast effects of limited and full interaction or examine how interaction affects contextual applicability. Because an important factor in child language acquisition is joint attention-the social interaction between caretaker and human infant concerning objects and actions in their environment-the authors contrasted training in which joint attention was present or absent (i.e., full vs. limited interaction) and found that 2 parrots did not learn in the absence of joint attention but did learn English labels when full interaction was present.

Social Malleability in Cowbirds: New Measures Reveal New Evidence of Plasticity in the Eastern Subspecies (Molothrus ater ater)

Abstract: The social experiences of young Molothrus ater ater cowbirds were manipulated in a 2-year study. In the 1 st year, males were housed with pairs of canaries. The males were tested in 3 social contexts. Also, vocal repertoires were recorded and played back to females. In contrast to a previous study of the M. a. artemisiae subspecies, the males did not vocalize to the canaries in courtship tests (T. M. Freeberg, A. P. King, & M. J. West, 1995) but showed incompetent courtship of female cowbirds. In their 2nd year, half of the males were housed with older males and female cowbirds, and half were housed with only females. Those exposed to older males courted much more successfully than did those deprived of such experience. All males developed new repertoires, and song potencies did not correlate across years. The data reveal intraspecific variation in the ontogeny of mate recognition but intraspecific dependence on social learning to acquire courtship skills. In the experiments reported here, we manipulated juvenile Molothrus ater ater cowbirds' opportunities for social and vocal interaction during their 1st and 2nd years. We bad three goals. First, we looked for intraspecific variation in the ontogeny of mate recognition in cowbirds. Second, we examined interrelationships between vocal capacity and vocal performance. Third, we investigated the role social experience with older conspecific males may play in consolidating the courtship skills of younger males.

Learning and male–male sexual competition in Japanese quail (Coturnix japonica).

Abstract: Male Japanese quail (Coturnix japonica) were trained individually to discriminate between 2 sounds presented at opposite ends of an outdoor aviary. One of the sounds (the positive conditioned stimulus [CS+]) was associated with the release of a female, and the other (the negative CS [CS-]) was presented alone. Which of the 2 sounds served as the CS+ (and which served as the CS-) was counterbalanced across subjects. The subjects came to approach their CS+ but did not move away from their CS-. After having been conditioned individually, the subjects were tested in pairs, with a single female released after the presentation of a stimulus that was the CS+ for one of the males and the CS- for the other male. During most of these tests, the male for whom the prefemale stimulus was the CS+ copulated with the female before the male for whom the prefemale stimulus was the CS-. These results indicate that learning can have an important role in competition for access to a reproductive partner.

Social Experience Affects the Process and Outcome of Vocal Ontogeny in Two Populations of Cowbirds (Molothrus ater)

Abstract: Longitudinal vocal records of 26 juvenile male cowbirds from 2 populations (Molothrus ater ater and Molothrus ater artemisiae) were analyzed to look for susceptibility to social influence from either female cowbirds or heterospecifics. Within each population, 1 group of males was individually housed with female conspecifics, and the other with pairs of canaries (Serinus canaria). Evidence was found for female influence in both populations. M. a. artemisiae males showed more vulnerability to heterospecific influence and developed song more slowly than did M. a. ater males. Greater vocal production was correlated with faster acquisition of song, especially for the males housed with female conspecifics. In that female cowbirds do not sing, these data indicate the inadequacy of mechanisms based on imitation to explain vocal ontogeny. The data also reinforce the need to consider the intraspecific impact of social and ecological parameters on vocal learning. The nature and the timing of vocal learning vary across populations of brown-headed cowbirds, as has been docu­ mented in laboratory and field studies (King & West, 1990; O'Logblen & Rothstein, 1993; Rothstein, Yokel, & Flei­ scher, 1986). No single pattern describes vocal ontogeny, either for songs (the focus of the present study) or for flight

Early auditory experience and the ontogeny of alarm-call discrimination in Belding's ground squirrels (Spermophilus beldingi).

Abstract: Because young ground squirrels are vulnerable to predation, selection would favor the early ability to respond to alarm calls. This requires discrimination of classes of alarm calls from each other as well as from non-alarm calls. Pre-emergent auditory experience may influence the development of discrimination. As a means of determining when Belding's ground squirrels (Spermophilus beldingi) can discriminate among calls, cardiac responses to alarm calls and control stimuli were recorded from 2 rearing groups that differed in the frequency of alarm-call exposure. Results suggest that before natal emergence, young can discriminate between 2 classes of alarm calls but they may not discriminate these calls from control stimuli. No differences in responses were found between the rearing groups; thus experience with calls may not influence the onset of discrimination. Early discrimination may facilitate the rapid development of post-emergent behavioral alarm-call responses. In many species of group-living birds and mammals, the appearance of a predator elicits vocalizations that can alert other animals of impending danger (for a review, see Klump & Shalter, 1984). These alarm calls may be especially important to individuals that have not already detected the predator, because the calls indicate that danger is imminent and quick action is required to reduce the likelihood of capture. Responding properly to alarm calls may be especially important to immature young, because they are generally more susceptible to predators than adults. Given that trial-and-error learning can be fatal, one might expect that inexperienced young would be able to respond appropriately to alarm calls the first time they heard such calls. This expectation raises the question of when and how young develop adaptive behavioral responses to alarm calls. To display such responses, young must first be able to discrim

A kinematic analysis of evasive dodging movements used during food protection in the rat (Rattus norvegicus): evidence for sex differences in movement.

Abstract: Food-deprived rats (Rattus norvegicus) will protect their food by dodging away from a conspecific. A detailed kinematic analysis of these movements in adult rats shows that each sex uses sex-typical movements. Females move their snout through a greater spatial curvature, and their snout achieves a greater velocity, relative to the pelvis, than males. Males make more hindpaw steps than females and achieve a more simultaneous movement of the fore- and hindquarters. This suggests that females pivot around a point more posterior on the body than males. The finding that functionally similar patterns of movement have a sex-specific organization provides a new dimension for the study of sex differences. These differences are discussed in relation to sex differences in sex-typical behaviors, associated body structure, and neural control.

Type of prenatal sensory experience affects prenatal auditory learning in bobwhite quail (Colinus virginianus).

Abstract: This study examined the effects of specific types of prenatal auditory stimulation on the auditory learning capacity of bobwhite embryos (Colinus virginianus) incubated in either communal or isolation conditions. Results revealed that socially incubated embryos could learn an individual bobwhite maternal call, whereas embryos denied physical and tactile stimulation as a result of isolation incubation failed to demonstrate prenatal auditory learning of the maternal call. In contrast, embryos exposed to bobwhite chick contentment calls in the period prior to hatching demonstrated prenatal auditory learning, whether they were incubated socially or in isolation. Socially incubated and isolation-incubated embryos exposed to bobwhite chick distress calls failed to learn the individual maternal call, indicating that the type of sensory stimulation the developing organism encounters prenatally is important in fostering normal perceptual learning ability.

A study of long-term odor memory in squirrel monkeys (Saimiri sciureus).

Abstract: Five squirrel monkeys (Saimiri sciureus) were trained to discriminate between pairs of odors, and their ability to recognize these as positive or negative was tested at intervals of up to 7 months. Retention was excellent up to 15 weeks and remained significantly above chance even after 30 weeks. Good performance at the shorter intervals was not due to rapid relearning, although at the longer intervals considerable savings were demonstrated by the animals' ability to reach criterion more rapidly than with novel odors. Thus, squirrel monkeys possess a robust memory for odors and show flat forgetting curves consistent with reports for human subjects.

Age differences in the ability of chimpanzees to distinguish mirror-images of self from video images of others.

Abstract: To evaluate Heyes's (1994) claim that chimpanzees are incapable of using mirrored information to obtain otherwise unavailable information about the self, we exposed two different age groups of chimpanzees (3-year-olds and 7- to 10-year-olds) to mirrors and video images of conspecifics. Their reactions to these stimuli were videotaped and were later scored for behavioral indices of self-recognition by a trained observer who was blind to the purpose and conditions of the study. Some types of behavior (contingent facial and body movements) were clearly influenced by the type of stimulus that the chimpanzees were viewing but not by age; however, other behaviors (self-exploration) were affected by age in conjunction with the type of stimulus the animals were viewing. The results suggest that, unlike self-exploratory behavior, contingent facial and body movements may not, by themselves, be reliable indicators of self-recognition.