Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning

Previous laboratory studies on social learning suggest that some animals can learn more readily if they first observe a conspecific demonstrator perform the task unsuccessfully and so fail to obtain a food reward than if they observe a successful demonstrator that obtains the food. This effect may indicate a difference in how easily animals are able to associate different outcomes with the conspecific or could simply be the result of having food present in only some of the demonstrations. To investigate we tested a scatter-hoarding mammal, the eastern grey squirrel, on its ability to learn to choose between two pots of food after watching a conspecific remove a nut from one of them on every trial. Squirrels that were rewarded for choosing the opposite pot to the conspecific chose correctly more frequently than squirrels rewarded for choosing the same pot (a feature-negative effect). Another group of squirrels was tested on their ability to choose between the two pots when the rewarded option was indicated by a piece of card. This time, squirrels showed no significant difference in their ability to learn to choose the same or the opposite pot. The results add to anecdotal reports that grey squirrels can learn by observing a conspecific and suggest that even when all subjects are provided with demonstrations with the same content, not all learning occurs equally. Prior experience or expectations of the association between a cue (a conspecific) and food influences what can be learned through observation whilst previously unfamiliar cues (the card) can be associated more readily with any outcome.     

Food and token quantity discrimination in capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>)

Quantity discrimination is adaptive in a variety of ecological contexts and different taxa discriminate stimuli differing in numerousness, both in the wild and in laboratory settings. Quantity discrimination between object arrays has been suggested to be more demanding than between food arrays but, to our knowledge, the same paradigm has never been used to directly compare them. We investigated to what extent capuchin monkeys’ relative numerousness judgments (RNJs) with food and token are alike. Tokens are inherently non-valuable objects that acquire an associative value upon exchange with the experimenter. Our aims were (1) to assess capuchins’ RNJs with food (Experiment 1) and with tokens (Experiment 2) by presenting all the possible pair-wise choices between one to five items, and (2) to evaluate on which of the two proposed non-verbal mechanisms underlying quantity discrimination (analogue magnitude and object file system) capuchins relied upon. In both conditions capuchins reliably selected the larger amount of items, although their performance was higher with food than with tokens. The influence of the ratio between arrays on performance indicates that capuchins relied on the same system for numerical representation, namely analogue magnitude, regardless of the type of stimuli (food or tokens) and across both the small and large number ranges.     

Token mediated tool exchange between tufted capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>)

Three experiments were conducted to test whether a pair of tufted capuchin monkeys (Cebus apella) could generalize their ability to exchange tokens and tool objects with a human experimenter to similar exchanges with a conspecific partner. Monkeys were tested in side-by-side enclosures, one enclosure containing a tool-use apparatus and one or more token(s), and the other enclosure containing one or more tool object(s). The monkeys willingly transferred tokens and tools to a conspecific with little practice. Following a small amount of training, we also found that the monkeys would select situation-appropriate tokens to exchange for specific tools, but did not select appropriate tool objects in response to another monkey’s token transfers. Implications regarding role reversal are discussed.     

Social facilitation of eating novel food in tufted capuchin monkeys (Cebus apella): input provided by group members and responses affected in the observer

Learning about food palatability from watching what conspecifics eat might be one of the advantages of group living. A previous study investigated whether group members' presence or eating activity account for social facilitation of eating of foods never previously tasted. Capuchins encountered novel colored foods when (1) alone (Alone condition) or (2) with group members visible in the nearby cage (Group-present condition) or (3) with group members present and eating a familiar food that had not been colored (Group+food condition). Social facilitation of eating occurred when group members were eating, despite the difference in color between the familiar food eaten by them and the novel food presented to the experimental subject. To clarify what subjects learnt from group members when social facilitation occurred, we further analyze here the data from the previous study. The number of visual exposures to the colored novel food (as a group member) correlated with increased consumption of that novel food when encountered later (as experimental subject). In contrast, the number of times that an individual fed on the familiar food (as a group member) did not decrease its consumption of novel food (as experimental subject). Therefore, capuchins (1) habituated to the colors of the novel foods, and (2) did not take into account that seeing group members eating a food does not provide information about the palatability of a differently colored food. Since social facilitation of eating occurs when foods do not match in color, at least in capuchins, social facilitation of eating should not be considered as a way of learning about a safe diet, but rather as a way of overcoming neophobia. Accepted after revision: 18 August 2001 Electronic Publication     

Capuchin monkeys are not prosocial in an instrumental helping task

Comparative research can shed light on the evolutionary roots and cognitive underpinnings of prosocial behavior by revealing not only positive instances of prosocial motivations in other species, but also the boundary conditions of these motivations. To explore factors that may constrain prosocial behavior, we examined whether brown capuchins (Cebus apella), which demonstrate regard for the welfare of conspecifics in other contexts, would behave prosocially in a minimal-cost instrumental helping task. We observed that when given the opportunity to share tokens that allow a conspecific to obtain food from an apparatus, capuchins showed no regard for another individual's welfare. Subjects transferred tokens to an adjacent chamber when the apparatus was present, but did so just as often when the chamber was empty as when there was a recipient present to obtain food. While capuchins are sensitive to others' welfare in some contexts, the current results suggest that they do not spontaneously produce goal-specific helping actions on behalf of a conspecific. The lack of regard for others exhibited in this context provides insights into the factors that may constrain prosocial behavior in capuchins and other primate species.     

Social learning in captive African elephants (Loxodonta africana africana)

Social learning is a more efficient method of information acquisition and application than trial and error learning and is prevalent across a variety of animal taxa. Social learning is assumed to be important for elephants, but evidence in support of that claim is mostly anecdotal. Using a herd of six adult female African bush elephants (Loxodonta africana africana) at the San Diego Zoo’s Safari Park, we evaluated whether viewing a conspecific’s interactions facilitated learning of a novel task. The tasks used feeding apparatus that could be solved in one of two distinct ways. Contrary to our hypothesis, the method the demonstrating animal used did not predict the method used by the observer. However, we did find evidence of social learning: After watching the model, subjects spent a greater percentage of their time interacting with the apparatus than they did in unmodeled trials. These results suggest that the demonstrations of a model may increase the motivation of elephants to explore novel foraging tasks.     

Capuchin monkeys’ use of human and conspecific cues to solve a hidden object-choice task

Learning by watching others can provide valuable information with adaptive consequences, such as identifying the presence of a predator or locating a food source. The extent to which nonhuman animals can gain information by reading the cues of others is often tested by evaluating responses to human gestures, such as a point, and less often evaluated by examining responses to conspecific cues. We tested whether ten brown capuchin monkeys (Cebus [Sapajus] apella) were able to use cues from monkeys and a pointing cue from a human to obtain hidden rewards. A monkey could gain access to a reward hidden in one of two locations by reading a cue from a conspecific (e.g., reaching) or a human pointing. We then tested whether they could transfer this skill from monkeys to humans, from humans to monkeys, and from one conspecific to another conspecific. One group of monkeys was trained and tested using a conspecific as the cue-giver and was then tested with a human cue-giver. The second group of monkeys was trained and tested with a human cue-giver and was then tested with a monkey cue-giver. Monkeys that were successful with a conspecific cue-giver were also tested with a novel conspecific cue-giver. Monkeys learned to use a human point and conspecific cues to obtain rewards. Monkeys that had learned to use the cues of a conspecific to obtain rewards performed significantly better than expected by chance when they were transferred to the cues of a novel conspecific. Monkeys that learned to use a human point to obtain rewards performed significantly better than expected by chance when tested while observing conspecific cues. Some evidence suggested that transferring between conspecific cue-givers occurred with more facility than transferring across species. Results may be explained by simple rules of association learning and stimulus generalization; however, spontaneous flexible use of gestures across conspecifics and between different species may indicate capuchins can generalize learned social cues within and partially across species.     

Copying without rewards: socially influenced foraging decisions among brown capuchin monkeys

An individual’s foraging activity can be influenced by the choices made by nearby conspecifics. The interest shown in the location and characteristics of a feeding patch may depend on the feeding success of a conspecific there, a process that needs to be distinguished from choices guided by rewards to the observer itself. We investigated how rewards for both self and others influence the foraging choices of captive capuchin monkeys (Cebus apella). Thirteen adult capuchins observed familiar female conspecific models explore one of three opaque boxes under three conditions. In the first, there were no rewards available to either monkey; in the second, rewards were available to the model only; and in the third, both monkeys could retrieve a reward. Under all conditions, subjects more often explored the same box as the model than was expected by chance. Thus, without ever receiving a reward themselves or without seeing another receive rewards, subjects’ searches were directed at the box explored by another monkey. The tendency to match the model’s choice increased if the subject was rewarded. We compared these results to control conditions in which the model was either absent, or present but not allowed to demonstrate. Subjects’ located the reward less often in control conditions, than in the experimental conditions. We conclude that extrinsic rewards, while helpful, are not required for partners to influence the foraging choices of capuchins, and that the unrewarded copying of foraging choices demonstrated here may provide the basis for additional social influences on learning. This contribution is part of the Special Issue “A Socioecological Perspective on Primate Cognition” (Cunningham and Janson 2007)     

Non‐generalized and generalized conditioned reinforcers: establishment and validation

Conditioned reinforcers, or tokens, are frequently used in clinical settings; however, little applied research has focused on establishing and validating their effectiveness. Following pairing of a novel token with an edible reinforcer in the present study, preference and reinforcer assessments verified that the tokens functioned as conditioned reinforcers. Results indicated that the tokens were established as conditioned reinforcers that matched the reinforcer value of the primary reinforcers with which they had been paired. The effects of motivating operations (MOs) on the effectiveness of these conditioned reinforcers were then evaluated. Conditioned reinforcer effectiveness decreased during satiation conditions. Subsequently it was found that increasing the number of backup reinforcers with which the token was paired resulted in the effectiveness maintaining during satiation conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental evidence for action imitation in killer whales (Orcinus orca)

Comparative experimental studies of imitative learning have focused mainly on primates and birds. However, cetaceans are promising candidates to display imitative learning as they have evolved in socioecological settings that have selected for large brains, complex sociality, and coordinated predatory tactics. Here we tested imitative learning in killer whales, Orcinus orca. We used a ‘do-as-other-does’ paradigm in which 3 subjects witnessed a conspecific demonstrator’s performance that included 15 familiar and 4 novel behaviours. The three subjects (1) learned the copy command signal ‘Do that’ very quickly, that is, 20 trials on average; (2) copied 100 % of the demonstrator’s familiar and novel actions; (3) achieved full matches in the first attempt for 8–13 familiar behaviours (out of 15) and for the 2 novel behaviours (out of 2) in one subject; and (4) took no longer than 8 trials to accurately copy any familiar behaviour, and no longer than 16 trials to copy any novel behaviour. This study provides experimental evidence for body imitation, including production imitation, in killer whales that is comparable to that observed in dolphins tested under similar conditions. These findings suggest that imitative learning may underpin some of the group-specific traditions reported in killer whales in the field.     

Learning words’ sounds before learning how words sound: 9-Month-olds use distinct objects as cues to categorize speech information

One of the central themes in the study of language acquisition is the gap between the linguistic knowledge that learners demonstrate, and the apparent inadequacy of linguistic input to support induction of this knowledge. One of the first linguistic abilities in the course of development to exemplify this problem is in speech perception: specifically, learning the sound system of one’s native language. Native-language sound systems are defined by meaningful contrasts among words in a language, yet infants learn these sound patterns before any significant numbers of words are acquired. Previous approaches to this learning problem have suggested that infants can learn phonetic categories from statistical analysis of auditory input, without regard to word referents. Experimental evidence presented here suggests instead that young infants can use visual cues present in word-labeling situations to categorize phonetic information. In Experiment 1, 9-month-old English-learning infants failed to discriminate two non-native phonetic categories, establishing baseline performance in a perceptual discrimination task. In Experiment 2, these infants succeeded at discrimination after watching contrasting visual cues (i.e., videos of two novel objects) paired consistently with the two non-native phonetic categories. In Experiment 3, these infants failed at discrimination after watching the same visual cues, but paired inconsistently with the two phonetic categories. At an age before which memory of word labels is demonstrated in the laboratory, 9-month-old infants use contrastive pairings between objects and sounds to influence their phonetic sensitivity. Phonetic learning may have a more functional basis than previous statistical learning mechanisms assume: infants may use cross-modal associations inherent in social contexts to learn native-language phonetic categories.     

A TOKEN SYSTEM FOR A CLASS OF UNDERACHIEVING HYPERACTIVE CHILDREN

Using a BAB design, a token system requiring cooperative interaction was used to change the reading and vocabulary performance of an 18-member class of third-grade hyperactive boys. Four different colored tokens, which could be exchanged for 15 minutes of play on electrovideo games, were earned by successful completion of two tasks that involved learning to read and to use new vocabulary words in sentences, and two tasks in which the student served as a proctor to a student who had not yet completed those tasks. The mean number of tasks completed during the intervention periods rose to over nine times the number completed during reversal. Additionally, the average completion rate for the school district's standardized weekly reading level examinations rose from four to eight fold during the token conditions. All 18 students responded to the token program by increasing their academic performance.     

Learning how to learn from social feedback: The origins of early vocal development

Infants’ prelinguistic vocalizations reliably organize vocal turn-taking with social partners, creating opportunities for learning to produce the sound patterns of the ambient language. This social feedback loop supporting early vocal learning is well-documented, but its developmental origins have yet to be addressed. When do infants learn that their non-cry vocalizations influence others? To test developmental changes in infant vocal learning, we assessed the vocalizations of 2- and 5-month-old infants in a still-face interaction with an unfamiliar adult. During the still-face, infants who have learned the social efficacy of vocalizing increase their babbling rate. In addition, to assess the expectations for social responsiveness that infants build from their everyday experience, we recorded caregiver responsiveness to their infants’ vocalizations during unstructured play. During the still-face, only 5-month-old infants showed an increase in vocalizing (a vocal extinction burst) indicating that they had learned to expect adult responses to their vocalizations. Caregiver responsiveness predicted the magnitude of the vocal extinction burst for 5-month-olds. Because 5-month-olds show a vocal extinction burst with unfamiliar adults, they must have generalized the social efficacy of their vocalizations beyond their familiar caregiver. Caregiver responsiveness to infant vocalizations during unstructured play was similar for 2- and 5-month-olds. Infants thus learn the social efficacy of their vocalizations between 2 and 5 months of age. During this time, infants build associations between their own non-cry sounds and the reactions of adults, which allows learning of the instrumental value of vocalizing.     

An experimental evaluation of tokens as conditioned reinforcers in retarded children

Since the publication of experimental reports by Wolfe (1936) and Cowles (1937), that tokens could be established as conditioned reinforcers, many accounts have appeared on the implementation of token systems in human subjects. Tokens have been successfully used as prosthetic motivational devices in a great variety of situations and subjects, such as retarded children (Birnbrauer, Wolf, Kidder and Tague, 1965), adult psychotics (Ayllon and Azrin, 1969), delinquent children and adolescents (Tyler, 1967; Phillips and Wolf, 1968), low achievers in schools (Clark, Lachowicz and Wolf, 1968), emotionally disturbed children (Hewett, Taylor and Artuso, 1969) and in normal classroom settings (O'Leary, Becker, Evans and Saudargas, 1969). In these reports, administration of tokens usually produced an increase in the frequency of desirable social and productive behavior. However, none of these studies showed that the effect of the tokens depended on their role as conditioned reinforcers based on the standard exchange systems being used. No assessment was provided about the separate contribution of the social reinforcement operations involved in dispensing tokens in a social setting.A suggestion about the possible confounding effects of social reinforcement in token administration comes from the failure to establish token systems in subjects who are partially unresponsive to social reinforcement (Hamblin et al., 1970; Ribes and Souza e Silva, in preparation). The present research was conducted with the aim of isolating the effects of conditioned reinforcement as such—apart from those produced by the social reinforcement provided in the delivery of tokens.     

Social blockade of taste-aversion learning in Norway rats (Rattus norvegicus): is it a social phenomenon?

In Experiment 1, hooded rats (Rattus norvegicus) were exposed to a novel diet in a food dish or on a conspecific; they were allowed to consume the same diet and then were injected with a toxin LiCl. Later both groups ate more of the novel diet than animals that had not been exposed, and the conspecific-exposed group ate more than the dish-exposed group. Reducing aversion learning by exposure on a conspecific is known as social blockade. We examined if this effect is because a conspecific intensifies dietary cues and thereby increases latent inhibition. Experiment 2 failed to show that diet on a conspecific is a more effective conditioned stimulus for taste-aversion learning than diet in a dish, and Experiment 3 showed that diet in a dish is an effective overshadowing stimulus in aversion learning but diet on a conspecific is not. These results suggest that social blockade cannot readily be assimilated to a latent-inhibition model and may be a distinctly social form of learning.     

Substitution effects in a generalized token economy with pigeons

Pigeons made repeated choices between earning and exchanging reinforcer‐specific tokens (green tokens exchangeable for food, red tokens exchangeable for water) and reinforcer‐general tokens (white tokens exchangeable for food or water) in a closed token economy. Food and green food tokens could be earned on one panel; water and red water tokens could be earned on a second panel; white generalized tokens could be earned on either panel. Responses on one key produced tokens according to a fixed‐ratio schedule, whereas responses on a second key produced exchange periods, during which all previously earned tokens could be exchanged for the appropriate commodity. Most conditions were conducted in a closed economy, and pigeons distributed their token allocation in ways that permitted food and water consumption. When the price of all tokens was equal and low, most pigeons preferred the generalized tokens. When token‐production prices were manipulated, pigeons reduced production of the tokens that increased in price while increasing production of the generalized tokens that remained at a fixed price. The latter is consistent with a substitution effect: Generalized tokens increased and were exchanged for the more expensive reinforcer. When food and water were made freely available outside the session, token production and exchange was sharply reduced but was not eliminated, even in conditions when it no longer produced tokens. The results join with other recent data in showing sustained generalized functions of token reinforcers, and demonstrate the utility of token‐economic methods for assessing demand for and substitution among multiple commodities in a laboratory context.     

Reducing Excessive Television Viewing

Excessive television watching among children can have several negative consequences, including exposure to frequent violent and aggressive scenes and limitations in their opportunities to engage in alternative educational and prosocial activities. In the present study, a youngster evidencing high levels of television viewing behavior was placed on a modified token economy: earned tokens were used to activate the television for set periods of time. With onset of the intervention, immediate and dramatic reductions in television viewing were noted. High levels returned during a return to baseline phase, but reductions again occured when the intervention was reimplmented. Positive second-order effects were noted in the child's school work, in the amounts of time the family spent together, and in the mother's perception of a social support variable.     

The effect of token reinforcement on McCarthy Scale performance for white preschoolers of low and high social position

In Study 1, the effect of making tokens contingent on correct performance of low social position preschoolers on the McCarthy Scales of Children's Abilitieswas examined. Preschoolers in a token reinforcement group scored significantly higher (mean=8 IQ points) than subjects in a control group. In Study 2, the effect of tokens on McCarthyresults was examined as a function of social position in a 2×2 design. The high social position control group scored significantly above the low social position control. The low social position token reinforcement group, however, performed as well as both the high social position control and token reinforcement groups. Use of systematic reinforcement contingencies to reduce test error is discussed.     

Token transfer between mother and offspring chimpanzees (Pan troglodytes): mother–offspring interaction in a competitive situation

Chimpanzees can flexibly use tokens in cognitive tasks, but it is still unknown if they can share and/or compete over tokens as they do for food. This study aimed to evaluate the interactions spontaneously occurring between mother and offspring chimpanzees when tokens exchangeable for food were provided. Forty tokens were scattered on the floor in an experimental playroom. Three mother and offspring chimpanzee pairs were tested. Each token was exchangeable for a piece of food in a vending machine installed on the wall of the playroom. In the beginning of the study, both mother and offspring took tokens and exchanged them for pieces of food independently. Later, two offspring started to take more tokens than their mothers. At that time, the offspring whimpered or cried more often than during earlier sessions. This behavior compelled the mothers to abstain from taking tokens. The mothers sometimes shared their tokens with their offspring, or were tolerant of their offspring taking their tokens from their hand. For one pair, the offspring sometimes shared tokens with her mother when her mother begged for the tokens. These results suggest that chimpanzees’ cognitive abilities enable them not only to use tokens, but also to compete for tokens, as they do for food. The results also suggest that token sharing between mother and offspring may be bidirectional and that transfer of tokens mainly occurs as a result of begging, although on some occasion offspring were able to obtain a token directly from his/her mother through tolerated scrounging.     

Fourteen-month-olds pay attention to vowels in novel words

Recent research has shown that infants are sensitive to mispronunciations of words when tested using a preferential looking task. The results of these studies indicate that infants are able to access the phonological detail of words when engaged in lexical recognition. However, most of this work has focused on mispronunciations of consonants in familiar and novel words. Very little is known about the role that vowels play in constraining lexical access during the early stages of lexical development. We describe a word learning study with 14- and 18-month-old infants that tests their sensitivity to mispronunciations of word-medial vowels using a preferential looking task. We found that both age groups demonstrated recognition of correctly pronounced tokens of the newly learnt words but not mispronounced tokens. These results indicate that vowels constrain lexical access of novel words by as early as 14 months of age, and add to the growing body of literature indicating that infants exploit detailed phonological information when processing both familiar and newly learnt words.