Chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) show the isolation effect during serial list recognition memory tests

The isolation effect (or von Restorff effect) occurs when one item in a to-be-remembered list is distinctive from all remaining items, and memory for that item is enhanced. Four chimpanzees were presented with a serial list of four photographs. In the homogeneous condition, all list items were from the same semantic category (e.g., four fruits). In the isolate condition, three items were from the same category, but the fourth item (the isolate) was from a different category (e.g., three fruits and one toy). Then, two photographs were presented, and the chimpanzees had to select the one that was from the list. Two of four chimpanzees were significantly more likely to select a correct isolate item than an item from the same list position in the homogeneous condition for at least some list positions. This facilitation in performance was for isolate items only, as presenting an isolate item in a list did not facilitate greater recognition of other list items compared to the homogeneous condition. These results indicated that some chimpanzees perceived the semantic categories of the photographs, and categorization of photographs led to the isolation effect. Thus, chimpanzees may share with humans some aspects of memory organization that involve spontaneously categorizing visual stimuli and recognizing categorically unique stimuli.     

Establishing a generalized repertoire of helping behavior in children with autism

The present study used a multiple baseline across participants design to assess whether 4 children with autism could learn a generalized repertoire of helping adults with different tasks through the use of a multicomponent teaching package. Different helping responses were taught in the presence of multiple exemplars of discriminative stimuli drawn from experimenter-defined categories of helping behavior (e.g., locating objects, putting away items, setting up an activity). During the training condition, video models, prompting, and reinforcement were used. The results showed that all 4 children learned to emit appropriate helping responses in the presence of discriminative stimuli from the helping categories used during training. Generalization of helping responses was observed in the presence of untrained discriminative stimuli during additional probe conditions. Additional pre- and postintervention generalization trials showed that the frequency of helping responses also increased in the presence of novel stimuli, in a novel setting, and with a novel instructor.     

How chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) perform in a modified emotional Stroop task

The emotional Stroop task is an experimental paradigm developed to study the relationship between emotion and cognition. Human participants required to identify the color of words typically respond more slowly to negative than to neutral words (emotional Stroop effect). Here we investigated whether chimpanzees (Pan troglodytes) would show a comparable effect. Using a touch screen, eight chimpanzees were trained to choose between two simultaneously presented stimuli based on color (two identical images with differently colored frames). In Experiment 1, the images within the color frames were shapes that were either of the same color as the surrounding frame or of the alternative color. Subjects made fewer errors and responded faster when shapes were of the same color as the frame surrounding them than when they were not, evidencing that embedded images affected target selection. Experiment 2, a modified version of the emotional Stroop task, presented subjects with four different categories of novel images: three categories of pictures of humans (veterinarian, caretaker, and stranger), and control stimuli showing a white square. Because visits by the veterinarian that include anaesthetization can be stressful for subjects, we expected impaired performance in trials presenting images of the veterinarian. For the first session, we found correct responses to be indeed slower in trials of this category. This effect was more pronounced for subjects whose last anaesthetization experience was more recent, indicating that emotional valence caused the slowdown. We propose our modified emotional Stroop task as a simple method to explore which emotional stimuli affect cognitive performance in nonhuman primates.     

Stimulus factors in the training of prepositional usage in three autistic children

Language deficient, autistic children were trained to use the prepositions "in" and "on". Three subjects were exposed to conditions of training that differed in the method of employment of stimulus objects used to train prepositional usage. Two subjects were trained first with "ambiguous" stimuli, that is, the same stimulus objects were used for training both prepositions. The two subjects were then switched to a training condition with "non-ambiguous" stimulus objects, that is, objects used for training "in" were different than those used for training "on". The two subjects were then switched to the ambiguous stimulus condition and finally returned again to training with non-ambiguous stimuli (four conditions). A third subject began with training on non-ambiguous stimuli, was switched to an ambiguous condition and was then switched back to non-ambiguous stimuli (three conditions). The results for two of the three subjects indicated that accurate usage of the two prepositions was obtained only under training conditions with non-ambiguous stimuli. Results for the third subject suggested that initial training with non-ambiguous stimuli might enhance subsequent accurate responding with ambiguous stimuli.     

Immediate and long-term retention of basic-level categories in 24-month-olds

This study assessed the effect of presenting single versus multiple exemplars of basic-level categories on 24-month-olds' long-term memory for categorical information. Sixty-four infants were tested in a paired-comparison recognition memory paradigm immediately and one week after familiarization with basic-level categories. Infants were randomly assigned to one of two familiarization conditions and one of two test conditions. In one familiarization condition (Varied Exemplar), they briefly viewed four different exemplars of each of 16 basic-level categories. In the other familiarization condition (Single Exemplar), they viewed only one instance of each category on four different trials. Test trials consisted of either an exemplar seen during familiarization (Familiar-Exemplar Test) or novel intracategory exemplar (Unfamiliar-Exemplar Test) paired with a stimulus from a novel category. Both immediately following familiarization and one week later, infants looked longer at test stimuli from the novel category irrespective of familiarization or test condition.     

Category-structure effects in picture comparisons

Subjects indicated for a series of trials whether or not two pictures of common objects were from the same category. Reaction time (RT) was recorded. The pool of stimuli used in the series of trials consisted of two pictures representing each of several categories. Half were S categories, members of which were similar; the other half were D categories, which had dissimilar members (this variable is termed category structure). In Experiments 1 and 3, the similarity manipulation defining category structure was based on the concept of basic level categories (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976). In Experiment 2, category labels were homonyms, and the two members of S or D categories represented one or two senses of the labels, respectively. The principal finding was an effect of category structure (faster RT on trials using stimuli from S categories rather than D categories). These results are interpreted in terms of a model that postulates the use of semantic codes in the task, even on trials where the two stimuli are physically identical.     

The translation effect in memory search

The function relating recognition reaction time to the size of a memorized set of items is steeper when the memorized items and the probe are in two different categories, related by a memorized translation scheme, than when they are in the same category. Experiment 1 demonstrates that this “translation effect” is obtained for both familiar and unfamiliar translation schemes and further demonstrates that the zero-intercepts of the functions are lower when the probe differs from the memorized items in category than when it does not. Experiment 2 demonstrates that the slopes of the functions relating negative RT to memorized set size when probe and set are the same in category are steeper than the slopes of the corresponding positive functions just in case subjects are aware that the probe and set categories may differ. Experiment 3 demonstrates that the translations between memorized items and a probe that differ in category are done during the rehearsal of the memorized set, not after the probe is presented. Arguments are presented that rehearsal strategy determines memory comparison time, presumably through a hypothetical memory strength variable, but that direct-access strength theories that deny a memory scanning process are inadequate to account for the data.     

Use of number by crows: investigation by matching and oddity learning

Hooded crows were trained in two-alternative simultaneous matching and oddity tasks with stimulus sets of three different categories: color (black and white), shape (Arabic Numerals 1 and 2, which were used as visual shapes only), and number of elements (arrays of one and two items). These three sets were used for training successively and repeatedly; the stimulus set was changed to the next one after the criterion (80% correct or better over 30 consecutive trials) was reached with the previous one. Training was continued until the criterion could be reached within the first 30 to 50 trials for each of the three training sets. During partial transfer tests, familiar stimuli (numerals and arrays in the range from 1 to 2) were paired with novel ones (numerals and arrays in the range from 3 to 4). At the final stage of testing only novel stimuli were presented (numerals and arrays in the range from 5 to 8). Four of 6 birds were able to transfer in these tests, and their performance was significantly above chance. Moreover, performance of the birds on the array stimuli did not differ from their performance on the color or shape stimuli. They were capable of recognizing the number of elements in arrays and comparing the stimuli by this attribute. It was concluded that crows were able to apply the matching (or oddity) concept to stimuli of numerical category.     

Spontaneous transfer of matching by infant chimpanzees (Pan troglodytes)

Four infant chimpanzees learned a matching-to-sample task when only two training stimuli were used. They then spontaneously transferred the matching concept to novel items, including three-dimensional objects and fabric swatches, without any experimenter-provided differential feedback. These results support the view that the matching concept is broadly construed by chimpanzees from the beginning and does not depend upon explicit training.     

特征的呈现方式对类别学习中规则和相似性知识获得的影响

采用原型变异任务,通过操纵规则和相似性特征的呈现通道,探讨特征的呈现方式对类别学习中规则和相似性知识获得的影响。结果发现,在听觉-视觉条件下习得规则的人数显著多于习得相似性的人数,而在视觉-听觉和视觉-视觉条件下则不存在显著差异;并且,三种条件下习得规则的正确率都高于习得相似性的正确率。这说明特征的呈现方式影响对规则和相似性特征的习得,在听觉通道呈现规则时被试更倾向基于规则分类。     

Categorization in infancy based on novelty and co-occurrence

Abstract categories (i.e., groups of objects that do not share perceptual features, such as food) abound in everyday situations. The present looking time study investigated whether infants are able to distinguish between two abstract categories (food and toys), and how this ability may extend beyond perceived information by manipulating object familiarity in several ways. Test trials displayed 1) the exact familiarized objects paired as they were during familiarization, 2) a cross-pairing of these same familiar objects, 3) novel objects in the same category as the familiarized items, or 4) novel objects in a different category. Compared to the most familiar test trial (i.e., Familiar Category, Familiar Objects, Familiar Pairings), infants looked longer to all other test trials. Although there was a linear increase in looking time with increased novelty of the test trials (i.e., Novel Category as the most novel test trial), the looking times did not differ significantly between the Novel Category and Familiar Category, Unfamiliar Objects trials. This study contributes to our understanding of how infants form object categories based on object familiarity, object co-occurrence, and information abstraction.     

Information about the logical structure of a category affects generalization

This paper considers whether information about the logical structure of a category affects how people generalize. We carried out three experiments with the following structure: participants were first presented with a set of training items, and were subsequently asked to decide whether new items belonged to the same category as the training items. Each experiment had two conditions that differed only in terms of the category label provided for the training items; different category labels conveyed different information about the logical structure of the category to which the training items were supposed to belong. In all cases, participants' generalization was greatly affected by such information. Our results suggest that people make the default assumption that category labels correspond to groupings of highly similar objects.     

Spontaneous discrimination of natural stimuli by chimpanzees (Pan troglodytes)

Six chimpanzees (Pan troglodytes) were presented with pairs of color photographic images of 5 different categories of animals (cat, chimp, gorilla, tiger, fish). The subjects responded to each pair using symbols for "same" and "different." Both within- and between-category discriminations were tested, and all chimpanzees classified the image pairs in accordance with the 5 experimenter-defined categories under conditions of nondifferential reinforcement. Although previous studies have demonstrated identification or discrimination of natural categories by nonhuman animals, subjects were typically differentially reinforced for their responses. The present findings demonstrate that chimpanzees can classify natural objects spontaneously and that such classifications may be similar to those that would be observed in human subjects.     

Long-term proactive interference and novelty enhancement effect in monkey list memory

Serial-probe-recognition (SPR) performance by 2 monkeys deteriorated over several months of training. Three hundred and twenty different items were presented without repetition within a session (trial unique) but were repeated between sessions. The cause of the deterioration was identified as proactive interference (PI) due to repetitive use of items from day to day. Introduction of novel stimuli across days improved performance from 63% to 82% correct (Experiment 1). Tests with only probe items and no list items (Experiment 2) revealed that the monkeys were using a familiar/novel response strategy in combination with a relational strategy (relating the probe item to the list items) to further improve their SPR performance. Intermixing familiar baseline trials and novel transfer trials within a session (Experiment 3) encouraged the subjects to use a relational strategy, and it improved performance on baseline trials as well as on transfer trials. Possible qualitative similarity between the relational strategy and the familiar/novel response strategy is discussed along with theoretical implications of these findings for experiments which have used small number of repeating stimuli within a session.     

Case-like categories in children: The actor and some related categories

Case categories were investigated using a method in which pictures are presented accompanied by a sentence describing the scene: Preschool children learn to put tokens on the objects in the pictures according to the role each object plays in the scene as described. Generalization trials explore what the children include within the various roles. Children rapidly learn to associate tokens with case-like categories during the training phase, and readily transfer to new stimuli in generalization trials. The experiments demonstrate that children have a broad Actor category. The Actor “does” the action, and Actors are not necessarily animate. However, animacy is a class property of stimuli to which the children were very sensitive. There was evidence that User and Instrument are subcategories of Actor that are differentiated only when a sentence contains both. The data also suggest a Locative category, and Patient as a category of the grammatical object. Finally, the children appeared to treat subjects of predicate adjectives as a separate category, here called the Subject of Attribution, distinct from Actor, and functionally independent of objects of transitive verbs.     

Category learning in the context of co-presented items

A series of four studies explore how the presentation of multiple items on each trial of a categorization task affects the course of category learning. In a three-category supervised classification task involving multi-dimensionally varying artificial organism-like stimuli, learners are shown a target plus two context items on every trial, with the context items’ category membership explicitly identified. These triads vary in whether one, two, or all three categories are represented. This presentation context can support within-category comparison and/or between-category contrast. The most successful learning occurs when all categories are represented in each trial. This pattern occurs across two different underlying category structures and across variations in learners’ prior knowledge of the relationship between the target and context items. These results appear to contrast with some other recent findings and make clear the potential importance of context-based inter-item evaluation in human category learning, which has implications for psychological theory and for real-world learning environments.     

Controlling relations in conditional discrimination and matching by exclusion.

Normally capable adults learned two-choice identity matching of three-digit numerals and arbitrary matching of physically dissimilar nonsense syllables. The stimuli were displayed on a computer terminal, and responses consisted of typing on the terminal's keyboard. In Experiment 1, every trial displayed a sample numeral, a comparison numeral, and three equal signs (= = =). The comparison stimulus was to be selected if it was identical with the sample; otherwise the equal sign was to be selected. This "single comparison" method was then used to show that arbitrary matching could be based upon either sample-S+ or sample-S- relations. In Experiment 2, a series of probe trials displayed a novel sample, a comparison stimulus from the arbitrary matching baseline, and = = =. Subjects typically selected = = =; they apparently were excluding the baseline comparison stimulus. Experiments 3 through 5 investigated which variables in training would lead to the selection of baseline comparison stimuli in response to novel samples. Behavior was usually unchanged when baseline training included relating comparison stimuli to as many as four different samples. Punishment contingencies were effective, but performance did not generalize unless those contingencies were applied in relation to more than one baseline comparison stimulus.     

Activation and integration of motor components in a short-term priming paradigm

The aim of the present research was to study the processes involved in knowledge emergence. In a short-term priming paradigm, participants had to categorize pictures of objects as either "kitchen objects" or "do-it-yourself tools". The primes and targets represented objects belonging to either the same semantic category or different categories (object category similarity), and their use involved gestures that were either similar or very different (gesture similarity). The condition with a SOA of 100ms revealed additive effects of motor similarity and object category similarity, whereas another condition with a SOA of 300ms showed an interaction between motor and category similarity. These results were interpreted in terms of the activation and integration processes involved in the emergence of mental representations.     

Discrimination of five-dimensional stimuli by pigeons: Limitations of feature analysis

Pigeons were trained to discriminate between stimuli constructed using five orthogonal two-valued features. The stimuli consisted of stylized monochrome drawings of seeds. Two different training procedures (conditional and simultaneous discrimination) were used. In the first two experiments, the discrimination required was between polymorphous categories, in which a positive stimulus was defined as one in which three or more of the five features took their positive values. Discrimination in both experiments was imperfect; the pigeons' behaviour only came under the control of a subset of the available features (one to three in Experiment 1, three or four in Experiment 2). In Experiment 3, single features had to be discriminated, while the remaining features varied. It was found that all five features of the “seed” stimuli could be discriminated, but one of them was exceptionally difficult. The results show that pigeons do not reliably use all the features available to them when making category discriminations. This casts doubts on feature analysis as a basis for the excellent performance pigeons show when required to discriminate between categories of natural objects.