Chimpanzees (Pan troglodytes) recognize spatial and object correspondences between a scale model and its referent

In the present study, the contributions of spatial and object features to chimpanzees' comprehension of scale models were examined. Seven chimpanzees that previously demonstrated the ability to use a scale model as an information source for the location of a hidden item were tested under conditions manipulating the feature correspondence and spatial-relational correspondence between objects in the model and an outdoor enclosure. In Experiment 1, subjects solved the task under two conditions in which one object cue (color or shape) was unavailable, but positional cues remained. Additionally, performance was above chance under a third condition in which both types of object cues, but not position cues, were available. In Experiment 2, 2 subjects solved the task under a condition in which shape and color object cues were simultaneously unavailable. The results suggest that, much like young children, chimpanzees are sensitive to both object and spatial-relational correspondences between a model and its referent.     

Confronting Math Stereotypes in the Classroom: Its Effect on Female College Students’ Sexism and Perceptions of Confronters

Women often face sexism and stereotypes about their academic ability, and this makes it important to examine the effects of confronting sexism in the college classroom. The current research consisted of 2 studies of how witnessing a confrontation of a sexist stereotype in the classroom affects female students’ perceptions of the confronters and self-reported sexism. The samples consisted of female students from a public college in the Northeastern U.S. who provided their perceptions of teachers described in vignettes as either confronting or not confronting a student’s stereotype of women as unskilled at math. In Study 1 (N?=?48) perceptions of the teacher were more positive when confronting the stereotype, and students’ self-reported sexism was reduced when the teacher confronted rather than ignored the stereotype. Study 2 (N?=?56) compared the effects of a teacher versus a student confrontation of the same stereotype. Participants perceived the teacher and student more positively when they confronted rather than ignored the stereotype. However, the source of the confrontation yielded no differences in sexism. These results suggest that students want their teachers to respond to bias in the classroom and that teachers should respond to sexist incidents in order to reduce the level of sexism among their students.     

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.     

Size matters: impact of item size and quantity on array choice by chimpanzees (Pan troglodytes)

The authors previously reported that chimpanzees (Pan troglodytes) showed a striking bias to select the larger of 2 candy arrays, despite a reversed reward contingency in which the animals received the smaller, nonselected array as a reward, except when Arabic numerals were used as stimuli. A perceptual or incentive-based interference occurred that was overcome by symbolic stimuli. The authors of the present study examined the impact of element size in choice arrays, using 1 to 5 large and small candies. Five test-sophisticated chimpanzees selected an array from the 2 presented during each trial. Their responses were not optimal, as animals generally selected arrays with larger total mass; thus, they received the smaller remaining array as a reward. When choice stimuli differed in size and quantity, element size was more heavily weighted, although choices reflected total candy mass. These results replicate previous findings showing chimpanzees' difficulties with quantity judgments under reverse reward contingencies and also show that individual item size exerts a more powerful interference effect.     

Predicting Prosocial Behavior Toward Sex-Trafficked Persons: The Roles of Empathy,Belief in a Just World,and Attitudes Toward Prostitution

Human trafficking has been identified as a global human rights violation. This study aimed to investigate the predictors of prosocial behaviors toward sex-trafficked persons. Participants were 223 undergraduates randomly assigned to read a vignette and answer follow-up questions along with measures of empathy, just world belief, attitudes toward prostitution, and proactive behavior. Empathy was highest for trafficked women, regardless of citizenship status. Trafficked foreign women received the highest empathy, and U.S. prostitutes received the least. Path analysis results indicate just world belief, beliefs about prostitutes, and family values relating to prostitution had direct effects on empathic concern; in turn, empathic concern had a direct effect on proactive behavior. Explanations for the results are discussed, along with educational and clinical implications.     

Biological explanations and stigmatizing attitudes: using essentialism and perceived dangerousness to predict antistigma intervention effectiveness

The theory of essentialism suggests that biological explanations of stigmatized behavior may not be effective at decreasing stigmatizing attitudes. The effects of biological explanations on stigmatizing attitudes were the topic of two experiments. In the first experiment, participants (N = 243) perceived a biological explanation as a less effective in relation to dangerousness and social distancing attitudes about mental illness than about homosexuality. The second experiment (N = 113) compared the effect of biological and free choice explanations on stigmatizing attitudes about abnormal sexual and eating behaviors. The results indicated that a biological explanation increased belief in essentialism and was most effective for attitudes related to anger and blame. These results suggest that the effectiveness of biological explanations as an antistigma tool varies according to the attitude and stigmatized group.     

Raking it in: the impact of enculturation on chimpanzee tool use

Recent evidence for different tool kits, proposed to be based upon culture-like transmission, have been observed across different chimpanzee communities across Western Africa. In light of these findings, the reported failures by seven captive juvenile chimpanzees tested with 27 tool use tasks (Povinelli 2000) seem enigmatic. Here we report successful performance by a group of nine captive, enculturated chimpanzees, and limited success by a group of six semi-enculturated chimpanzees, on two of the Povinelli tasks, the Flimsy Tool task, and the Hybrid Tool task. All chimpanzees were presented with a rake with a flimsy head and a second rake with a rigid head, either of which could be used to attempt to retrieve a food reward that was out of reach. The rigid rake was constructed such that it had the necessary functional features to permit successful retrieval, while the flimsy rake did not. Both chimpanzee groups in the present experiment selected the functional rigid tool correctly to use during the Flimsy Tool task. All animals were then presented with two “hybrid rakes” A and B, with one half of each rake head constructed from flimsy, non-functional fabric, and the other half of the head was made of wood. Food rewards were placed in front of the rigid side of Rake A and the flimsy side of Rake B. To be successful, the chimps needed to choose the rake that had the reward in front of the rigid side of the rake head. The fully enculturated animals were successful in selecting the functional rake, while the semi-enculturated subjects chose randomly between the two hybrid tools. Compared with findings from Povinelli, whose non-enculturated animals failed both tasks, our results demonstrate that chimpanzees reared under conditions of semi-enculturation could learn to discriminate correctly the necessary tool through trial-and-error during the Flimsy Tool task, but were unable to recognize the functional relationship necessary for retrieving the reward with the “hybrid” rake. In contrast, the enculturated chimpanzees were correct in their choices during both the Flimsy Tool and the Hybrid Tool tasks. These results provide the first empirical evidence for the differential effects of enculturation on subsequent tool use capacities in captive chimpanzees.     

Constructive and deconstructive tool modification by chimpanzees (Pan troglodytes)

Nine chimpanzees (Pan troglodytes) were tested for their ability to assemble or disassemble the appropriate tool to obtain a food reward from two different apparatus. In its deconstructed form, the tool functioned as a probe for one apparatus. In its constructed form, the tool functioned as a hook, appropriate for a second apparatus. Each subject completed four test trials with each apparatus type. Tool types were randomized and counter-balanced between the two forms. Results demonstrated that adult and juvenile chimpanzees (N = 7) were successful with both tool types, while two infant chimpanzees performed near chance. Off-line video analyses revealed that tool modifications followed by attempted solutions by the adults and juveniles were typically correct on the first attempt. Neither infant was successful in modifying tools correctly on the first attempt over all eight trials. The older chimpanzees’ ability to modify the appropriate tool consistently prior to use indicates an immediate recognition of the functional attributes necessary for the successful use of tool types on each apparatus, and represents a non-replication of a previously reported study by Povinelli.