Analogical reasoning in a capuchin monkey (Cebus apella)

Previous evidence has suggested that analogical reasoning (recognizing similarities among object relations when the objects themselves are dissimilar) is limited to humans and apes. This study investigated whether capuchin monkeys (Cebus apella) can use analogical reasoning to solve a 3-dimensional search task. The task involved hiding a food item under 1 of 2 or 3 plastic cups of different sizes and then allowing subjects to search for food hidden under the cup of analogous size in their own set of cups. Four monkeys were exposed to a series of relational matching tasks. If subjects reached criterion on these tasks, they were exposed to relational transfer tasks involving novel stimuli. Three of the monkeys failed to reach criterion on the basic relational matching tasks and therefore were not tested further. One monkey, however, revealed above-chance performance on a series of transfer tasks with 3 novel stimuli. This evidence suggests that contrary to previous arguments, a member of a New World monkey species can solve an analogical problem.     

Token-mediated tool-use by a tufted capuchin monkey (Cebus apella)

This research examined token-mediated tool-use in a tufted capuchin monkey (Cebus apella). We conducted five experiments. In experiment 1 we examined the use of plastic color-coded chips to request food, and in experiments 2–5 we examined the use of color-coded chips to request tools. Our subject learned to use chips to request tools following the same general pattern seen in great apes performing analogous tasks, that is, initial discrimination followed by an understanding of the relationship among tokens, tools, and their functions. Our findings are consistent with the view that parallel representational processes underlie the tool-related behavior of capuchins and great apes. Received: 11 March 1998 / Accepted after revision: 19 August 1998     

Instance-based automaticity and aging: acquisition, reacquisition, and long-term retention

This research examined age differences in the acquisition and reacquisition of instance-based automaticity. In 2 experiments, young and older adults were trained to enumerate targets presented in otherwise empty displays or in displays that contained distractors. Experiment 1 revealed that older adults required more practice to reach asymptote than young adults. For both age groups, modifications of the identities and locations of targets produced substantial disruptions in performance, whereas modifications of the identities or locations of distractors produced little interference. However, no age differences in the representations of instances in memory were obtained in participants who reached asymptote. Experiment 2 revealed age deficits in the long-term retention and rate of reacquisition of instance-based automaticity 18 months after initial training.     

Medial auditory thalamus inactivation prevents acquisition and retention of eyeblink conditioning

The auditory conditioned stimulus (CS) pathway that is necessary for delay eyeblink conditioning was investigated using reversible inactivation of the medial auditory thalamic nuclei (MATN) consisting of the medial division of the medial geniculate (MGm), suprageniculate (SG), and posterior intralaminar nucleus (PIN). Rats were given saline or muscimol infusions into the MATN contralateral to the trained eye before each of four conditioning sessions with an auditory CS. Rats were then given four additional sessions without infusions to assess savings from the initial training. All rats were then given a retention test with a muscimol infusion followed by a recovery session. Muscimol infusions through cannula placements within 0.5 mm of the MGm prevented acquisition of eyeblink conditioned responses (CRs) and also blocked CR retention. Cannula placements more than 0.5 mm from the MATN did not completely block CR acquisition and had a partial effect on CR retention. The primary and secondary effects of MATN inactivation were examined with 2-deoxy-glucose (2-DG) autoradiography. Differences in 2-DG uptake in the auditory thalamus were consistent with the cannula placements and behavioral results. Differences in 2-DG uptake were found between groups in the ipsilateral auditory cortex, basilar pontine nuclei, and inferior colliculus. Results from this experiment indicate that the MATN contralateral to the trained eye and its projection to the pontine nuclei are necessary for acquisition and retention of eyeblink CRs to an auditory CS.     

Operant conditioning of eye movement in the monkey (Macaca nemestrina)

With the horizontal electrooculographic potential as the operant, four monkeys (Macaca nemestrina) were conditioned to move their eyes at high and low rates by initial use of fixed-ratio schedules of reinforcement, followed by a changeover to multiple schedules of fixed-ratio reinforcement and discriminated differential reinforcement of low rate. These differences in rate of eye movement were not observed in a control animal given the same patterns of discriminative stimuli and deliveries of the reinforcing agent independent of its eye movements.     

Socially learned preferences for differentially rewarded tokens in the brown capuchin monkey (Cebus apella)

Social learning is assumed to underlie traditions, yet evidence indicating social learning in capuchin monkeys (Cebus apella), which exhibit traditions, is sparse. The authors tested capuchins for their ability to learn the value of novel tokens using a previously familiar token-exchange economy. Capuchins change their preferences in favor of a token worth a high-value food reward after watching a conspecific model exchange 2 differentially rewarded tokens, yet they fail to develop a similar preference after watching tokens paired with foods in the absence of a conspecific model. They also fail to learn that the value of familiar tokens has changed. Information about token value is available in all situations, but capuchins seem to pay more attention in a social situation involving novel tokens.     

Repeated acquisition and discrimination reversal in the squirrel monkey (Saimiri sciureus)

Repeated acquisition and discrimination reversal tasks are often used to examine behavioral relations of, respectively, learning and cognitive flexibility. Surprisingly, despite their frequent use in cognitive neuroscience and behavioral pharmacology, variables that control performance under these two tasks have not been widely studied. The present studies were conducted to directly investigate the controlling variables in nonhuman primates. Squirrel monkeys were trained with a touchscreen variant of the repeated acquisition task in which a novel pair of S⁺/S^? stimuli was presented daily. Subjects learned to discriminate the two stimuli (acquisition) and, subsequently, with the contingencies switched (reversal). Results indicate that rates of both acquisition and reversal learning increased across successive sessions, but that rate of reversal learning remained slower than acquisition learning, i.e., more trials were needed for mastery. Subsequent experiments showed this difference between the rate of learning novel discriminations and reversal was reliable for at least 5 days between acquisition and reversal and notwithstanding the interpolation of additional discriminations. Experimental analysis of the S⁺/S^? elements of the tasks revealed that the difference in the rate of learning could not be attributed to a relatively aversive quality of the S^? or to a relatively appetitive quality of the S⁺, but, rather, to contextual control by the S⁺/S^? stimulus complex. Thus, if either element (S⁺ or S^?) of the stimulus complex was replaced by a novel stimulus, the rate of acquisition approximated that expected with a novel stimulus pair. These results improve our understanding of fundamental features of discrimination acquisition and reversal.     

Social influences on the acquisition of tool-using behaviors in tufted capuchin monkeys (Cebus apella)

To identify behaviors related to acquisition of tool-use in tufted capuchins (Cebus apella), we presented two tool-using tasks to two groups, extending findings by Westergaard and Fragaszy (1987) and Visalberghi (in press). Five Ss learned to use the tools in each task. The primary predictor of success was level of interest in the task. Observation of others at the apparatus did not facilitate exploratory behaviors or contact with the tools in the observers. Most animals performed exploratory behaviors more often when they were at the apparatus alone than when with another, whether or not the other was using a tool. Observers were quick to learn the relationship between another's activities and the appearance of food. We conclude that capuchins do not readily learn about instrumental relations by observation of others or imitate other's acts. Imitation probably plays no role in the spread of novel instrumental behaviors among monkeys.     

Sensitization and aversive conditioning: Effects on the startle reflex and electrodermal responding

Animal data suggest that shock sensitization as well as aversive learning potentiates the acoustic startle reflex. The present experiment tested, whether this shock sensitization also occurs in human subjects and whether it precedes aversive conditioning. Sixty subjects viewed—prior to conditioning—a series of slides of different emotional contents including the to be conditioned stimuli (CSs). Afterwards, the experimenter attached the shock electrodes and initiated shock exposure. Then, subjects were randomly assigned to view a series of two slides, each for eight acquisition trials in which one slide was followed by a shock. Subsequently, extinction trials (12 for each slide) were administered. During preconditioning, acquisition, and extinction, startle probes occurred unpredictably during and between slide viewing. Preconditioning data replicated previous results by Lang and his associates, showing that the startle response magnitude is directly related to the affective valence induced by the slides. Shock exposure strongly facilitated the startle reflex magnitude. This shock sensitization was absent for the skin conductance response. Course of learning also varied for both response systems. The data suggest that startle reflex potentiation indexes the acquisition of an avoidance disposition, which is preceded by a general sensitization of the protective reflexes. Skin conductance learning follows arousal changes and is modulated by cognitive processes.     

Instrumental conditioning of scratching in the laboratory rat

Experiment 1 demonstrates that scratching in the laboratory rat can be instrumentally conditioned with food reinforcement. However, the asymptotic rate of performance of this response is shown to be low, as compared with an instrumental lever press response. It is suggested that one reason for this low rate of responding is that the scratch response can only be performed in the presence of an infrequently occurring itch stimulus. In support of this account the remaining experiments demonstrate that the rate of instrumental scratching can be increased relative to that shown by control groups by using a technique which might be supposed to increase the frequency at which an itch stimulus occurs.     

Hemispheric asymmetry and electrodermal activity in orienting and pavlovian conditioning paradigms

Three experiments on lateralization of electrodermal orienting and conditioned behavior are reported. The basic findings show effects of hemispheric asymmetry on initial magnitude and rate of habituation of phasic stimulus-elicited electrodermal responses. In summary, responses to verbal stimuli repeatedly flashed to the right visual half-field are larger than corresponding responses in the left half-field. Similarily, spatially relevant stimuli initially presented to the left half-field result in larger responses than when the same stimuli are repeatedly presented in the right half-field. In the auditory modality, data show asymmetrical control of responding to verbal material in a dichotic conditioning paradigm with greater resistance to extinction when the conditioned stimulus is initially fed only to the left hemisphere as compared to when it is fed only to the right hemisphere. It is argued that the present approach taps on basic mechanisms for the lateralization of attentional and associative functions.