Quantity estimation and comparison in western lowland gorillas (Gorilla gorilla gorilla)

We investigated the quantity judgment abilities of two adult male western lowland gorillas (Gorilla gorilla gorilla) by presenting discrimination tasks on a touch-screen computer. Both gorillas chose the larger quantity of two arrays of dot stimuli. On some trials, the relative number of dots was congruent with the relative total area of the two arrays. On other trials, number of dots was incongruent with area. The gorillas were first tested with static dots, then with dots that moved within the arrays, and finally on a task where they were required to discriminate numerically larger subsets within arrays of moving dots. Both gorillas achieved above-chance performance on both congruent and incongruent trials with all tasks, indicating that they were able to use number as a cue even though ratio of number and area significantly controlled responding, suggesting that number was not the only relevant dimension that the gorillas used. The pattern of performance was similar to that found previously with monkeys and chimpanzees but had not previously been demonstrated in gorillas within a computerized test format, and with these kinds of visual stimuli.     

Example‐based learning: Effects of model expertise in relation to student expertise

Background. Worked examples are very effective for novice learners. They typically present a written‐out ideal (didactical) solution for learners to study. Aims. This study used worked examples of patient history taking in physiotherapy that presented a non‐didactical solution (i.e., based on actual performance). The effects of model expertise (i.e., worked example based on advanced, third‐year student model or expert physiotherapist model) in relation to students' expertise (i.e., first‐ or second‐year) were investigated. Sample. One hundred and thirty‐four physiotherapy students (61 first‐year and 73 second‐year). Methods. Design was 2×2 factorial with factors ‘Student Expertise’ (first‐year vs. second‐year) and ‘Model Expertise’ (expert vs. advanced student). Within expertise levels, students were randomly assigned to the Expert Example or the Advanced Student Example condition. All students studied two examples (content depending on their assigned condition) and then completed a retention and test task. They rated their invested mental effort after each example and test task. Results. Second‐year students invested less mental effort in studying the examples, and in performing the retention and transfer tasks than first‐year students. They also performed better on the retention test, but not on the transfer test. In contrast to our hypothesis, there was no interaction between student expertise and model expertise: all students who had studied the Expert examples performed better on the transfer test than students who had studied Advanced Student Examples. Conclusions. This study suggests that when worked examples are based on actual performance, rather than an ideal procedure, expert models are to be preferred over advanced student models.     

Do chimpanzees learn reputation by observation? Evidence from direct and indirect experience with generous and selfish strangers

Can chimpanzees learn the reputation of strangers indirectly by observation? Or are such stable behavioral attributions made exclusively by first-person interactions? To address this question, we let seven chimpanzees observe unfamiliar humans either consistently give (generous donor) or refuse to give (selfish donor) food to a familiar human recipient (Experiments 1 and 2) and a conspecific (Experiment 3). While chimpanzees did not initially prefer to beg for food from the generous donor (Experiment 1), after continued opportunities to observe the same behavioral exchanges, four chimpanzees developed a preference for gesturing to the generous donor (Experiment 2), and transferred this preference to novel unfamiliar donor pairs, significantly preferring to beg from the novel generous donors on the first opportunity to do so. In Experiment 3, four chimpanzees observed novel selfish and generous acts directed toward other chimpanzees by human experimenters. During the first half of testing, three chimpanzees exhibited a preference for the novel generous donor on the first trial. These results demonstrate that chimpanzees can infer the reputation of strangers by eavesdropping on third-party interactions.     

Gender differences in the variability of lower extremity kinematics during treadmill locomotion

The authors examined whether there were gender differences in the variability of basic gait parameters (stride length, stride time) and 3-dimensional (3D) rotations of the hip, knee, and ankle joints during treadmill locomotion of 18 men and 15 women at 4 different gait speeds (walking at 5 km/hr, running at 8, 10, and 12 km/hr). The authors used 2-way analyses of variance to assess the data. No gender differences in the mean values or variability of basic gait parameters were detected. However, the women exhibited lower variability than did the men for 6 individual joint rotations: (a) transverse plane rotations of the ankle joint at 8, 10, and 12 km/hr, (b) transverse plane rotations of the hip and knee joints at 12 km/hr, and (c) sagittal plane rotations of the ankle joint at 12 km/hr. When collapsed across all 3D lower extremity rotations, the data showed that the women had lower variability than did the men at 12 km/hr. Reduced variability may result in more localized mechanical stress on anatomical structures and could therefore be a risk factor for injury in women at high gait speeds. The results also suggested that gender differences in variability may not be consistent across different levels of the motor system.     

Dispositional attribution: multiple inferences about motive-related traits

This research views dispositional inference as a process whereby perceivers integrate multiple inferences about a target person's motives and traits. The findings suggest that although perceived motives may stimulate extra attributional processing (S. Fein, 1996), the content of the inferred motive is important as well. Perceivers learned about situational forces implying that a target person had free choice, no choice, or an ulterior motive for helpful behavior. Inferences about the target's helpfulness differed depending on whether the target's behavior was attributed to an obedience motive (no-choice condition) or to a selfish motive (ulterior-motive condition). In general, inferences about motives were more predictive of dispositional inferences than were global causal attributions (to situational vs. dispositional forces) or base rate assumptions.     

Picture object recognition in an American black bear (<Emphasis Type="Italic">Ursus americanus</Emphasis>)

Many animals have been tested for conceptual discriminations using two-dimensional images as stimuli, and many of these species appear to transfer knowledge from 2D images to analogous real life objects. We tested an American black bear for picture-object recognition using a two alternative forced choice task. She was presented with four unique sets of objects and corresponding pictures. The bear showed generalization from both objects to pictures and pictures to objects; however, her transfer was superior when transferring from real objects to pictures, suggesting that bears can recognize visual features from real objects within photographic images during discriminations.