Species packing and the competition function with illustrations from coral reef fish.
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Performance-based measures of hand preference have been developed as an objective method of examining handedness. Previous research using this method showed that both skill demands and the position of the object in working space affect preferential hand reaching. Specifically, preferred hand reaches predominated in left hemispace, in spite of the biomechanical inefficiency involved in reaching across the body midline. This was mediated by the skill demands, with a higher frequency of preferred hand reaches for tasks requiring more skill. To further examine this issue, we increased the task skill demands. Twenty-two right-handed adults reached for five tools located in an array of five positions in front of them. Participants were required to pick up the tool, pick up and demonstrate how to use it, or pick up and actually use the tool on the materials provided. The results showed that the frequency of right hand reaches was greatest for the tool use condition. This effect was mediated by the position of the object in hemispace, with more right hand reaches occurring for the Use task in left hemispace than the other tasks, in support of our previous work.
There is little experimental evidence that any non-human species is capable of purposefully attempting to manipulate the psychological states of others deceptively (e.g., manipulating what another sees). We show here that chimpanzees, one of humans' two closest primate relatives, sometimes attempt to actively conceal things from others. Specifically, when competing with a human in three novel tests, eight chimpanzees, from their first trials, chose to approach a contested food item via a route hidden from the human's view (sometimes using a circuitous path to do so). These findings not only corroborate previous work showing that chimpanzees know what others can and cannot see, but also suggest that when competing for food chimpanzees are skillful at manipulating, to their own advantage, whether others can or cannot see them.
BACKGROUND: The RESIDential Environment project (RESIDE) is a longitudinal study evaluating the impact of a new residential design code on walking. OBJECTIVE: To develop a reliable measure of walking--undertaken within and outside the neighborhood--and overall physical activity. METHODS: A test-retest reliability study was undertaken (n = 82, mean age 39 years). The instrument was based on the International Physical Activity Questionnaire (IPAQ-short version) and Active Australia Survey. It measured usual frequency and duration of (1) recreational- and transport-related walking within and outside the neighborhood and (2) other vigorous and moderate physical activities. RESULTS: Reliability of recall of whether participants had walked within (k = 0.84) and outside (0.73) the neighborhood was acceptable. Similarly, recall of frequency and duration of transport and recreational-related walking within the neighborhood was excellent (ICC > or = 0.82), as was recall of transport-related walking trips outside the neighborhood (ICC > or = 0.84). Reliability for duration of recreational walking outside the neighborhood was fair to good (ICC = 0.55). The reliability of indices of total physical activity based on MET min/week (ICC = 0.82) and MET min/week dichotomized to 'sufficient' physical activity for health (kappa = 0.67) were both acceptable. CONCLUSIONS: The Neighborhood Physical Activity Questionnaire (NPAQ) is sufficiently reliable for studies examining environmental correlates of walking within the neighborhood.
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This study investigated the role of the hippocampus in pigeons learning of a food-related choice task. The effects of lesions induced by ibotenic acid were analyzed in two experiments. Experiment 1 investigated the effects of hippocampal damage on postoperative memory retrieval and in reversal learning. Experiment 2 investigated the effects of hippocampal lesions on the acquisition and reversal of learning. In both experiments probe tests were used to assess the behavioral strategies underlying the choice. In Experiment 1 hippocampal lesions impaired the preoperative learned performance in terms of choice latency but not choice accuracy. Experiment 2 data showed that, in postoperative learning sessions, latency as well as choice accuracy were impaired by hippocampal damage. The probe tests, in which a curtain was placed around the chamber, revealed behavioral patterns of a non-mapping strategy. This was true in both experiments and groups (experimental and controls). Immediately after training, during the probe tests of both experiments, in which food cups were omitted, the three groups spent more time in the target quadrant. However, immediately after the reversal condition, neither hippocampal damaged nor control pigeons showed a preference for the target quadrant. This may be interpreted as evidence for a hippocampal role in stimulus location learning involving non-mapping strategies.
Finding one's way in a large-scale environment may engage different cognitive processes than following a familiar route. The neural bases of these processes were investigated using functional MRI (fMRI). Subjects found their way in one virtual-reality town and followed a well-learned route in another. In a control condition, subjects followed a visible trail. Within subjects, accurate wayfinding activated the right posterior hippocampus. Between-subjects correlations with performance showed that good navigators (i.e., accurate wayfinders) activated the anterior hippocampus during wayfinding and head of caudate during route following. These results coincide with neurophysiological evidence for distinct response (caudate) and place (hippocampal) representations supporting navigation. We argue that the type of representation used influences both performance and concomitant fMRI activation patterns.
The authors report a novel approach to testing episodic-like memory for single events. Pigeons were trained in separate sessions to match the identity of a sample on a touch screen, to match its location, and to report on the length of the retention interval. When these 3 tasks were mixed randomly within sessions, birds were more than 80% correct on each task. However, performance on 2 different tests in succession after each sample was not consistent with an integrated memory for sample location, time, and identity. Experiment 2 tested binding of location and identity memories in 2 different ways. The results were again consistent with independent feature memories. Implications for tests of episodic-like memory are discussed.
In order to survive, small burrowing mammals need to remember the locations of escape burrows. Therefore, it is important to know what types of landmarks are used to aid navigation in the wild. The author tested the ability of free-ranging Columbian ground squirrels (Spermophilus columbianus) to locate escape burrows when local (e.g., vegetation pattern, local relief), global (e.g., forest edge, mountain outline), or both types of landmarks were obstructed. Results suggest that squirrels need both local and global landmarks of the environment for successful navigation, and that the upper portion of the horizon is especially important for orientation. Moreover, the lack of information from one type of landmark (local or global) cannot be completely compensated by the other type.
We asked whether honeybees, Apis mellifera, could solve a transitive inference problem. Individual free-flying bees were conditioned with four overlapping premise pairs of five visual patterns in a multiple discrimination task (A+ vs. B-, B+ vs. C-, C+ vs. D-, D+ vs. E-, where + and - indicate sucrose reward or absence of it, respectively). They were then tested with the nonadjacent pairs A vs. E and B vs. D. Preference of B to D is consistent with the use of the implicit hierarchy A > B > C > D > E. Equal choice of B and D supports choice based on the associative strength of the stimuli. The bees' choice was determined by their memory constraints: experience with the last premise pair (D+ vs. E-) predominated. In the tests, bees preferred A to E and chose equally B and D. An analysis of the performance in terms of a reward/penalty ratio showed that B had a higher associative strength than D. Thus, bees do not establish transitive inferences but, rather, guide their choices by the joint action of a recency effect and the associative strength of the stimuli. The former supports choice of D, whereas the latter supports choice of B, thus determining equal choice of B and D in the tests.
The developmental progression of play behavior was studied cross-sectionally in 85 children at eight age-levels between nine and 30 months. In a structured play situation, three major play patterns were distinguished: (1) exploratory play (at the end of the first year); (2) functional play (beginning of second year); and (3) representational play (after 15 months). Sequential play first occurred at 21 months. Play behavior with spatial characteristics was also observed: relational and container play between nine and 15 months, and understanding of spatial relationships, stacking and grouping between 18 and 24 months. There was a significant relationship between spontaneous and imitative play behavior; the greatest affect was displayed when the demonstrated behaviors matched the child's developmental level of play.
PURPOSE: Mongolian gerbils (Meriones unguiculatus) seize in response to sensory stimulation and forced exploratory behavior, but the incidence and severity of their seizures are variable. We wished to characterize the seizure pattern of gerbils from our breeding colony. METHODS: Ninety-three gerbils aged 1-16 months were tested for a mean of 24 consecutive weeks and assigned to a category according to their seizure pattern. Frequency distribution histograms of the mean scores assigned every 5 weeks were plotted for each category. Mean age, number of seizures, onset of the first facial and forelimb myoclonus, and of the first generalized tonic-clonic seizure (GTCS) were compared among categories. We performed correlation analysis between onset of seizures and animal age. RESULTS: From the 93 tested, no seizure-resistant gerbils could be isolated. Four major categories were distinguished. Category 1, highly seizure-sensitive gerbils (39%), exhibited seizures from the first few weeks of test on. Category 2, consisting of approximately 37%, were seizure-free for the first three to six consecutive tests, later developing facial and forelimb myoclonus and eventually GTCS. Because such progressive development of seizures was similar to that occurring upon electrical kindling, the gerbils were classified as kindled-like (KL). Among KL gerbils, older individuals were significantly more refractory to seizures. In category 3, gerbils (10%) exhibited inconsistent seizure behavior. Category 4 consisted of significantly younger animals (11%) with rapid progress to generalized seizures. CONCLUSIONS: Seizures of progressive severity can be induced in adult gerbils with a prolonged test regimen. As a consequence, the number of regularly seizing gerbils in a colony can be increased. Prolonged tests starting at a defined age may help characterize seizure development better in this genetic model of limbic epilepsy.
Two methods of assessing personal space in young children were examined in a group of 24 boys and 24 girls, aged 3 to 6 yr. When sex of peer figures and affect attributed to them were varied, 3-yr.-olds made distance-cue judgements based on affect but failed to use affect cues in structuring personal space. However, 4- to 6-yr.-olds readily perceived and used distance to communicate the affective quality of peer relations. On both measures, perception of distance cues increased with age. Only girls also used sex of figures as a social cue in depicting appropriate distances.
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Two experiments examined adult humans' folk physics (i.e., their naturally occurring and spontaneous understanding of the physical world) using variations of trap-table problems used to study chimpanzees' folk physics. When presented with these problems, people unnecessarily avoided retrieving a reward by pulling a rake on the side of a table with a trapping hole--even though it was highly unlikely that the hole would trap the reward. However, when the distance between the reward and the trap was sufficiently large and the distance that the reward had to travel to be retrieved was sufficiently short, people preferred to retrieve a reward by pulling the rake on the side of the table with the trap. These results underscore that behavior during tool-use tasks has many possible causes, only one of which might be a subject's folk physics.
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