Stages of category learning in monkeys (Macaca mulatta) and humans (Homo sapiens).

Smith and Minda (1998) and Blair and Homa (2001) studied the time course of category learning in humans. They distinguished an early, abstraction-based stage of category learning from a later stage that incorporated a capacity for categorizing exceptional category members. The present authors asked whether similar processing stages characterize the category learning of nonhuman primates. Humans (Homo sapiens) and monkeys (Macaca mulatta) participated in category-learning tasks that extended Blair and Homa’s paradigm comparatively. Early in learning, both species improved on typical items more than on exception items, indicating an initial mastery of the categories’ general structure. Later in learning, both species selectively improved their exception-item performance, indicating exception-item resolution or exemplar memorization. An initial stage of abstraction-based category learning may characterize categorization across a substantial range of the order Primates. This default strategy may have an adaptive resonance with the family resemblance organization of many natural-kind categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rules and resemblance: Their changing balance in the category learning of humans (Homo sapiens) and monkeys (Macaca mulatta).

In an early dissociation between intentional and incidental category learning, Kemler Nelson (1984) gave participants a categorization task that could be performed by responding either to a single-dimensional rule or to overall family resemblance. Humans learning intentionally deliberately adopted rule-based strategies; humans learning incidentally adopted family resemblance strategies. The present authors replicated Kemler Nelson’s human experiment and found a similar dissociation. They also extended her paradigm so as to evaluate the balance between rules and family resemblance in determining the category decisions of rhesus monkeys. Monkeys heavily favored the family resemblance strategy. Formal models showed that even after many sessions and thousands of trials, they spread attention across all stimulus dimensions rather than focus on a single, criterial dimension that could also produce perfect categorization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of artificial categories structured by family resemblances: A comparative study in people (Homo sapiens) and pigeons (Columba livia).

Adult humans (Homo sapiens) and pigeons (Columba livia) were trained to discriminate artificial categories that the authors created by mimicking 2 properties of natural categories. One was a family resemblance relationship: The highly variable exemplars, including those that did not have features in common, were structured by a similarity network with the features correlating to one another in each category. The other was a polymorphous rule: No single feature was essential for distinguishing the categories, and all the features overlapped between the categories. Pigeons learned the categories with ease and then showed a prototype effect in accord with the degrees of family resemblance for novel stimuli. Some evidence was also observed for interactive effects of learning of individual exemplars and feature frequencies. Humans had difficulty in learning the categories. The participants who learned the categories generally responded to novel stimuli in an all-or-none fashion on the basis of their acquired classification decision rules. The processes that underlie the classification performances of the 2 species are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The comparative psychology of same-different judgments by humans (Homo sapiens) and monkeys (Macaca mulatta).

The authors compared the performance of humans and monkeys in a Same-Different task. They evaluated the hypothesis that for humans the Same-Different concept is qualitative, categorical, and rule-based, so that humans distinguish 0-disparity pairs (i.e., same) from pairs with any discernible disparity (i.e., different); whereas for monkeys the Same-Different concept is quantitative, continuous, and similarity-based, so that monkeys distinguish small-disparity pairs (i.e., similar) from pairs with a large disparity (i.e., dissimilar). The results supported the hypothesis. Monkeys, more than humans, showed a gradual transition from same to different categories and an inclusive criterion for responding Same. The results have implications for comparing Same-Different performances across species--different species may not always construe or perform even identical tasks in the same way. In particular, humans may especially apply qualitative, rule-based frameworks to cognitive tasks like Same-Different. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus monkeys (macaca mulatta) immediately generalize the uncertain response.

Rhesus monkeys (Macaca mulatta) have learned, like humans, to use an uncertain response adaptively under test conditions that create uncertainty, suggesting a metacognitive process by which human and nonhuman primates may monitor their confidence and alter their behavior accordingly. In this study, 4 rhesus monkeys generalized their use of the uncertain response, without additional training, to 2 familiar tasks (2-choice discrimination learning and mirror-image matching to sample) that predictably and demonstrably produce uncertainty. The monkeys were significantly less likely to use the uncertain response on trials in which the answer might be known. These results indicate that monkeys, like humans, know when they do not know and that they can learn to use a symbol as a generalized means for indicating their uncertainty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stage 6 object concept in nonhuman primate cognition: A comparison between gorilla (Gorilla gorilla gorilla) and Japanese macaque (Macaca fuscata).

Several investigators have reported the achievement of Stage 6 object concept in a number of species of nonhuman primates. Because Stage 6 object concept implies a capacity for mental representation, such an achievement would demonstrate the presence of a crucial capacity in nonhuman primate cognition. There are, it is suggested, problems in the way nonhuman primates have been tested for Stage 6 object concept (i.e., that the tasks employed could be solved in nonrepresentational ways). The present study attempted to differentiate between representational and nonrepresentational responses in the typical task used for testing Stage 6 object concept (following the invisible displacements of an object). The performance of 2 22-mo-old Ss, a Japanese macaque and a gorilla, was compared. It was found that only the gorilla solved the task with the use of mental representation. The macaque consistently tried to solve the task by employing practical, nonrepresentational strategies. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The learning of exclusive-or categories by monkeys (Macaca mulatta) and humans (Homo sapiens).

A central question in categorization research concerns the categories that animals and humans learn naturally and well. Here, the authors examined monkeys' (Macaca mulatta) and humans' (Homo sapiens) learning of the important class of exclusive-or (XOR) categories. Both species exhibited—through a sustained level of ongoing errors—substantial difficulty learning XOR category tasks at 3 stimulus dimensionalities. Clearly, both species brought a linear-separability constraint to XOR category learning. This constraint illuminates the primate category-learning system from which that of humans arose, and it has theoretical implications concerning the evolution of cognitive systems for categorization. The present data also clarify the role of exemplar-specific processes in fully explaining XOR category learning, and suggest that humans sometimes overcome their linear-separability constraint through the use of language and verbalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning rule-described and non-rule-described categories: A comparison of children and adults.

Three experiments investigated the ability of 3-, 5-, and 8-year-old children as well as adults to learn sets of perceptual categories. Adults and children performed comparably on categories that could be learned by either a single-dimensional rule or by associative learning mechanisms. However, children showed poorer performance relative to adults in learning categories defined by a disjunctive rule and categories that were nonlinearly separable. Increasing the task demands for adults resulted in child-like performance on the disjunctive categories. Decreasing the task demands for children resulted in more adult-like performance on the disjunctive categories. The authors interpret these results within a multiple-systems approach to category learning and suggest that children have not fully developed the same explicit category learning system as adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical intuitions about support relations in monkeys (Macaca fuscata) and apes (Pan troglodytes).

Nonhuman primates, like humans, have demonstrated various physical intuitions. Cacchione and Krist (2004) examined chimpanzees' intuitions about support relations with the violation-of-expectation task. They reported that the chimpanzees possessed intuitions about support, but their intuitions differed from those of humans in part; they were sensitive to “contact/no-contact” and “amount of contact” but not “type of contact” rule. To further explore intuitions about support in nonhuman primates, we conducted similar experiments on monkeys (Japanese monkeys) and apes (chimpanzees). In three experiments, we presented physically possible and impossible events of different support relations to the participants and measured their looking times. The results reveal that the chimpanzees and monkeys detect the violations of “contact/no-contact” and “amount of contact” but not “type of contact” variable. Therefore, the apes and monkeys possess similar intuitions; however, these intuitions differ in part from those of humans. The present study provides new and corroborative evidence of intuitions about support in nonhuman primates. However, this again leads to the question of distinctive understanding about support relations among primate species. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects on executive function following damage to the prefrontal cortex in the rhesus monkey (Macaca mulatta).

[Correction Notice: An erratum for this article was reported in Vol 123(3) of Behavioral Neuroscience (see record 2009-07961-027). There was an error in the first sentence of the third full paragraph in the text on p. 235. The sentence should read “Based on the lesion reconstructions it was determined, as intended, that all monkeys had complete damage to areas 46, 8a, 8b, 9 and slight damage to area 10.”] Executive function is a term used to describe the cognitive processes subserved by the prefrontal cortex (PFC). An extensive body of work has characterized the effects of damage to the PFC in nonhuman primates, but it has focused primarily on the capacity of recognition and working memory. One limitation in studies of the functional parcellation of the PFC has been the absence of tests that assess executive function or its functional components. The current study used an adaptation of the Wisconsin Card Sorting Test, a classic test of frontal lobe and executive function in humans, to assess the effects of bilateral lesions in the dorsolateral PFC on executive function in the rhesus monkey (Macaca mulatta). The authors used the category set-shifting task, which requires the monkey to establish a pattern of responding to a specific category (color or shape) based on reward contingency, maintain that pattern of responding, and then shift to responding to a different category when the reward contingency changes. Rhesus monkeys with lesions of the dorsolateral PFC were impaired in abstraction, establishing a response pattern to a specific category and maintaining and shifting that response pattern on the category set-shifting task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid detection of snakes by Japanese monkeys (Macaca fuscata): An evolutionarily predisposed visual system.

Humans appear extremely sensitive to biologically threatening stimuli, such as snakes. In visual search tasks, humans respond to pictures of snakes faster than pictures of flowers. The authors report that macaque monkeys (Macaca fuscata), reared in a laboratory and with no experience with snakes, respond, as do humans, to pictures of snakes among flowers faster than vice versa (Experiment 1). This was also the case when grayscale pictures were used (Experiment 2). These results provide the first evidence of enhanced visual detection of evolutionarily relevant threat stimuli in nonhuman primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Effects on executive function following damage to the prefrontal cortex in the rhesus monkey (Macaca mulatta)": Correction to Moore et al (2009).

Reports an error in "Effects on executive function following damage to the prefrontal cortex in the rhesus monkey (Macaca mulatta)" by Tara L. Moore, Stephen P. Schettler, Ronald J. Killiany, Douglas L. Rosene and Mark B. Moss (Behavioral Neuroscience, 2009[Apr], Vol 123[2], 231-241). There was an error in the first sentence of the third full paragraph in the text on p. 235. The sentence should read “Based on the lesion reconstructions it was determined, as intended, that all monkeys had complete damage to areas 46, 8a, 8b, 9 and slight damage to area 10.” (The following abstract of the original article appeared in record 2009-04037-001.) Executive function is a term used to describe the cognitive processes subserved by the prefrontal cortex (PFC). An extensive body of work has characterized the effects of damage to the PFC in nonhuman primates, but it has focused primarily on the capacity of recognition and working memory. One limitation in studies of the functional parcellation of the PFC has been the absence of tests that assess executive function or its functional components. The current study used an adaptation of the Wisconsin Card Sorting Test, a classic test of frontal lobe and executive function in humans, to assess the effects of bilateral lesions in the dorsolateral PFC on executive function in the rhesus monkey (Macaca mulatta). The authors used the category set-shifting task, which requires the monkey to establish a pattern of responding to a specific category (color or shape) based on reward contingency, maintain that pattern of responding, and then shift to responding to a different category when the reward contingency changes. Rhesus monkeys with lesions of the dorsolateral PFC were impaired in abstraction, establishing a response pattern to a specific category and maintaining and shifting that response pattern on the category set-shifting task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category learning deficits in Parkinson's disease.

Sixteen patients with Parkinson's disease (PD), 15 older controls (OCs), and 109 younger controls (YCs) were compared in 2 category-learning tasks. Participants attempted to assign colored geometric figures to 1 of 2 categories. In rule-based tasks, category membership was defined by an explicit rule that was easy to verbalize, whereas in information-integration tasks, there was no salient verbal rule and accuracy was maximized only if information from 3 stimulus components was integrated at some predecisional stage. The YCs performed the best on both tasks. The PD patients were highly impaired compared with the OCs, in the rule-based categorization task but were not different from the OCs in the information-integration task. These results support the hypothesis that learning in these 2 tasks is mediated by functionally separate systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus macaques (Macaca mulatta) as living fossils of hominoid personality and subjective well-being.

Personality dimensions capturing individual differences in behavior, cognition, and affect have been described in several species, including humans, chimpanzees, and orangutans. However, comparisons between species are limited by the use of different questionnaires. We asked raters to assess free-ranging rhesus macaques at two time points on personality and subjective well-being questionnaires used earlier to rate chimpanzees and orangutans. Principal-components analysis yielded domains we labeled Confidence, Friendliness, Dominance, Anxiety, Openness, and Activity. The presence of Openness in rhesus macaques suggests it is an ancestral characteristic. The absence of Conscientiousness suggests it is a derived characteristic in African apes. Higher Confidence and Friendliness, and lower Anxiety were prospectively related to subjective well-being, indicating that the connection between personality and subjective well-being in humans, chimpanzees, and orangutans is ancestral in catarrhine primates. As demonstrated here, each additional species studied adds another fold to the rich, historical story of primate personality evolution. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Auditory discrimination of chord-based spectral structures by European starlings (Sturnus vulgaris).

European starlings (Sturnus vulgaris) were trained to discriminate two complex harmonic structures modeled after musical chords in a 2-alternative choice task. Musical chords provide rich acoustic structures with which to study relative pitch perception and perceptual invariance in nonhuman animals. The starlings learned the chord discrimination and transferred the discrimination to chords with different root frequencies, thus showing perceptual invariance for the chords. Further transfer tests showed that correlates of chord structure were indeed controlling discrimination performance. The proposition that the starlings were responding primarily to a sensory dimension of consonance and dissonance in the acoustic structures provides a good account of the data. The harmonic principles that govern consonance and dissonance may be important for starling auditory communication and, perhaps, auditory communication of other songbirds. From the standpoint of human music cognition, the data add to previous observations suggesting that the idea of musical universals may be extended to species other than humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Supervised and unsupervised learning of multidimensional acoustic categories.

Learning to recognize the contrasts of a language-specific phonemic repertoire can be viewed as forming categories in a multidimensional psychophysical space. Research on the learning of distributionally defined visual categories has shown that categories defined over 1 dimension are easy to learn and that learning multidimensional categories is more difficult but tractable under specific task conditions. In 2 experiments, adult participants learned either a unidimensional or a multidimensional category distinction with or without supervision (feedback) during learning. The unidimensional distinctions were readily learned and supervision proved beneficial, especially in maintaining category learning beyond the learning phase. Learning the multidimensional category distinction proved to be much more difficult and supervision was not nearly as beneficial as with unidimensionally defined categories. Maintaining a learned multidimensional category distinction was only possible when the distributional information that identified the categories remained present throughout the testing phase. We conclude that listeners are sensitive to both trial-by-trial feedback and the distributional information in the stimuli. Even given limited exposure, listeners learned to use 2 relevant dimensions, albeit with considerable difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facial expression categorization by chimpanzees using standardized stimuli.

The ability to recognize and accurately interpret facial expressions are critical social cognition skills in primates, yet very few studies have examined how primates discriminate these social signals and which features are the most salient. Four experiments examined chimpanzee facial expression processing using a set of standardized, prototypical stimuli created using the new ChimpFACS coding system. First, chimpanzees were found to accurately discriminate between these expressions using a computerized matching-to-sample task, and recognition was impaired for all but one expression category when they were inverted. Third, a multidimensional scaling analysis examined the perceived dissimilarity among these facial expressions revealing 2 main dimensions, the degree of mouth closure and extent of lip-puckering and retraction. Finally, subjects were asked to match each facial expression category using only individual component features. For each expression category, at least 1 component movement was more salient or representative of that expression than the others. However, these were not necessarily the only movements implicated in subject's overall pattern of errors. Therefore, similar to humans, both configuration and component movements are important during chimpanzee facial expression processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning and retention through predictive inference and classification.

Work in category learning addresses how humans acquire knowledge and, thus, should inform classroom practices. In two experiments, we apply and evaluate intuitions garnered from laboratory-based research in category learning to learning tasks situated in an educational context. In Experiment 1, learning through predictive inference and classification were compared for fifth-grade students using class-related materials. Making inferences about properties of category members and receiving feedback led to the acquisition of both queried (i.e., tested) properties and nonqueried properties that were correlated with a queried property (e.g., even if not queried, students learned about a species' habitat because it correlated with a queried property, like the species' size). In contrast, classifying items according to their species and receiving feedback led to knowledge of only the property most diagnostic of category membership. After multiple-day delay, the fifth-graders who learned through inference selectively retained information about the queried properties, and the fifth-graders who learned through classification retained information about the diagnostic property, indicating a role for explicit evaluation in establishing memories. Overall, inference learning resulted in fewer errors, better retention, and more liking of the categories than did classification learning. Experiment 2 revealed that querying a property only a few times was enough to manifest the full benefits of inference learning in undergraduate students. These results suggest that classroom teaching should emphasize reasoning from the category to multiple properties rather than from a set of properties to the category. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sociality and social learning in two species of corvids: The pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana).

The hypothesis that social learning is an adaptive specialization for social living predicts that social species should learn better socially than they do individually, but that nonsocial species should not exhibit a similar enhancement of performance under social learning conditions. The authors compared individual and social learning abilities in 2 corvid species: the highly social pinyon jay (Gymnorhinus cyanocephalus) and the less social Clark's nutcracker (Nucifraga columbiana). The birds were tested on 2 different tasks under individual and social learning conditions. Half learned a motor task individually and a discrimination task socially; the other half learned the motor task socially and the discrimination task individually. Pinyon jays learned faster socially than they did individually, but nutcrackers performed equally well under both learning conditions. Results support the hypothesis that social learning is an adaptive specialization for social living in pinyon jays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)