| Home | << 1 2 3 4 5 6 7 8 9 10 >> |
|
Zentall, T. R., Sherburne, L. M., Roper, K. L., & Kraemer, P. J. (1996). Value transfer in a simultaneous discrimination appears to result from within-event pavlovian conditioning. J Exp Psychol Anim Behav Process, 22(1), 68–75.
Abstract: When pigeons acquire a simple simultaneous discrimination, some of the value acquired by the S+ transfers to the S-. The mechanism underlying this transfer of value was examined in three experiments. In Experiment 1, pigeons trained on two simultaneous discriminations (A + B- and C +/- D-) showed a preference for B over D. This preference was reduced, however, following the devaluation of A. In Experiment 2, when after the same original training, value was given to D, the pigeons' preference for C did not significantly increase. In Experiment 3, when both discriminations involved partial reinforcement (S +/-), A + C- training resulted in a preference for B over D, whereas B + D- training resulted in a preference for A over C. Thus, simultaneous discrimination training appears to result in bidirectional within-event conditioning involving the S+ and S-.
|
|
Hampton, R. R., & Shettleworth, S. J. (1996). Hippocampus and memory in a food-storing and in a nonstoring bird species. Behav Neurosci, 110(5), 946–964.
Abstract: Food-storing birds maintain in memory a large and constantly changing catalog of the locations of stored food. The hippocampus of food-storing black-capped chickadees (Parus atricapillus) is proportionally larger than that of nonstoring dark-eyed juncos (Junco hyemalis). Chickadees perform better than do juncos in an operant test of spatial non-matching-to-sample (SNMTS), and chickadees are more resistant to interference in this paradigm. Hippocampal lesions attenuate performance in SNMTS and increase interference. In tests of continuous spatial alternation (CSA), juncos perform better than chickadees. CSA performance also declines following hippocampal lesions. By itself, sensitivity of a given task to hippocampal damage does not predict the direction of memory differences between storing and nonstoring species.
|
|
Hampton, R. R., & Shettleworth, S. J. (1996). Hippocampal lesions impair memory for location but not color in passerine birds. Behav Neurosci, 110(4), 831–835.
Abstract: The effects of hippocampal complex lesions on memory for location and color were assessed in black-capped chickadees (Parus atricapillus) and dark-eyed juncos (Junco hyemalis) in operant tests of matching to sample. Before surgery, most birds were more accurate on tests of memory for location than on tests of memory for color. Damage to the hippocampal complex caused a decline in memory for location, whereas memory for color was not affected in the same birds. This dissociation indicates that the avian hippocampus plays an important role in spatial cognition and suggests that this brain structure may play no role in working memory generally.
|
|
Sekuler, A. B., Lee, J. A., & Shettleworth, S. J. (1996). Pigeons do not complete partly occluded figures. Perception, 25(9), 1109–1120.
Abstract: One of the most common obstacles to object perception is the fact that objects often occlude parts of themselves and parts of other objects. Perceptual completion has been studied extensively in humans, and researchers have shown that humans do complete partly occluded objects. In an effort to understand more about the mechanisms underlying completion, recent research has extended the study of perceptual completion to other mammalian species. Monkeys and mice also seem to complete two-dimensional representations of partly occluded objects. The present study addresses the question of whether this capacity generalizes to a nonmammalian species, the pigeon (Columba livia). The results point to a limit of the generalizability of perceptual completion: pigeons do not complete partly occluded figures.
Keywords: Animals; *Columbidae; *Visual Perception
|
|
Whiten, A., Custance, D. M., Gomez, J. C., Teixidor, P., & Bard, K. A. (1996). Imitative learning of artificial fruit processing in children (Homo sapiens) and chimpanzees (Pan troglodytes). J Comp Psychol, 110(1), 3–14.
Abstract: Observational learning in chimpanzees and young children was investigated using an artificial fruit designed as an analog of natural foraging problems faced by primates. Each of 3 principal components could be removed in 2 alternative ways, demonstration of only one of which was watched by each subject. This permitted subsequent imitation by subjects to be distinguished from stimulus enhancement. Children aged 2-4 years evidenced imitation for 2 components, but also achieved demonstrated outcomes through their own techniques. Chimpanzees relied even more on their own techniques, but they did imitate elements of 1 component of the task. To our knowledge, this is the first experimental evidence of chimpanzee imitation in a functional task designed to simulate foraging behavior hypothesized to be transmitted culturally in the wild.
|
|
Waran, N. K., Robertson, V., Cuddeford, D., Kokoszko, A., & Marlin, D. J. (1996). Effects of transporting horses facing either forwards or backwards on their behaviour and heart rate. Vet. Rec., 139(1), 7–11.
Abstract: The effects of transporting horses facing either forwards or backwards were compared by transporting six thoroughbred horses in pairs in a lorry on one journey facing in the direction of travel, and on another journey facing away from the direction of travel, over a standard one-hour route. Heart rate monitors were used to record their heart rate before, during and after the journey and the horses' behaviour was recorded by scan sampling each horse every other minute. The average heart rate was significantly lower (P < 0.05) when the horses were transported facing backwards, and they also tended to rest on their rumps more (P = 0.059). In the forward-facing position, the horses moved more frequently (P < 0.05) and tended to hold their necks in a higher than normal position and to vocalise more frequently (P = 0.059). During loading the average peak heart rate was 38 bpm lower (P < 0.05) when the horses were backed into the horse box for rear-facing transport than when they were loaded facing forwards. However, there was no difference between transport facing forwards or backwards in terms of the peak unloading heart rate, or the average heart rate during loading or unloading. The horses seemed to find being transported less physically stressful when they were facing backwards than when they were facing forwards.
Keywords: Animals; *Behavior, Animal; Female; *Heart Rate; *Horses; Male; Posture/*physiology; *Transportation
|
|
Fulhorst, C. F., Hardy, J. L., Eldridge, B. F., Chiles, R. E., & Reeves, W. C. (1996). Ecology of Jamestown Canyon virus (Bunyaviridae: California serogroup) in coastal California. Am J Trop Med Hyg, 55(2), 185–189.
Abstract: This paper reports the first isolation of Jamestown Canyon (JC) virus from coastal California and the results of tests for antibody to JC virus in mammals living in coastal California. The virus isolation was made from a pool of 50 Aedes dorsalis females collected as adults from Morro Bay, San Luis Obispo County, California. The virus isolate was identified by two-way plaque reduction-serum dilution neutralization tests done in Vero cell cultures. Sera from the mammals were tested for antibody to JC virus by a plaque-reduction serum dilution neutralization method. A high prevalence of JC virus-specific antibody was found in horses and cattle sampled from Morro Bay. This finding is additional evidence for the presence of a virus antigenically identical or closely related to JC virus in Morro Bay and indicates that the vectors of the virus in Morro Bay feed on large mammals. A high prevalence of virus-specific antibody was also found in horses sampled from Marin and San Diego counties. This finding suggests that viruses antigenically identical or closely related to JC virus are geographically widespread in coastal California.
Keywords: Aedes/virology; Animals; Antibodies, Viral/blood; California/epidemiology; Cattle; Cattle Diseases/epidemiology; Deer; Dog Diseases/epidemiology; Dogs; Encephalitis Virus, California/immunology/*isolation & purification; Encephalitis, California/epidemiology/*veterinary; Female; Horse Diseases/epidemiology; Horses; Insect Vectors/virology; Lagomorpha; Male; Neutralization Tests/veterinary; Peromyscus; Rodent Diseases/epidemiology; Sigmodontinae
|
|
Cilnis, M. J., Kang, W., & Weaver, S. C. (1996). Genetic conservation of Highlands J viruses. Virology, 218(2), 343–351.
Abstract: We studied molecular evolution of the mosquito-borne alphavirus Highlands J (HJ) virus by sequencing PCR products generated from 19 strains isolated between 1952 and 1994. Sequences of 1200 nucleotides including portions of the E1 gene and the 3' untranslated region revealed a relatively slow evolutionary rate estimated at 0.9-1.6 x 10(-4) substitutions per nucleotide per year. Phylogenetic trees indicated that all HJ viruses descended from a common ancestor and suggested the presence of one dominant lineage in North America. However, two or more minor lineages probably circulated simultaneously for periods of years to a few decades. Strains isolated from a horse suffering encephalitis, and implicated in a recent turkey outbreak, were not phylogenetically distinct from strains isolated in other locations during the same time periods. Our findings are remarkably similar to those we obtained previously for another North American alphavirus, eastern equine encephalomyelitis virus, with which Highlands J shares primary mosquito and avian hosts, geographical distribution, and ecology. These results support the hypotheses that the duration of the transmission season affects arboviral evolutionary rates and vertebrate host mobility influences genetic diversity.
Keywords: Alphavirus/*genetics; Alphavirus Infections/transmission/veterinary/virology; Amino Acid Sequence; Animals; Base Sequence; Conserved Sequence; Disease Outbreaks; Encephalitis, Viral/veterinary/virology; *Evolution, Molecular; Horses; Molecular Sequence Data; Phylogeny; RNA, Viral/genetics; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Nucleic Acid; Turkeys; Variation (Genetics)/*genetics
|
|
Atwill, E. R., Mohammed, H. O., & Lopez, J. W. (1996). Evaluation of travel and use as a risk factor for seropositivity to Ehrlichia risticii in horses of New York state. Am J Vet Res, 57(3), 272–277.
Abstract: OBJECTIVES--To determine whether mean annual frequency and destination of equine travel was associated with exposure to Ehrlichia risticii and whether these associations were modified by horses' place of residence. DESIGN--Cross-sectional study. SAMPLE POPULATION--511 equine operations containing 2,587 horses were visited in New York state from a target population of 39,000 operations. PROCEDURE--Each horse was tested for serum antibodies against E risticii, using indirect fluorescent antibody. Information on the horse's travel history, farm's management practices, and surrounding ecology was obtained by personal interview and resource maps. Statistical analyses were performed on 2 cohorts of animals: all horses enrolled in the study and horses born on the property or that resided at least 4 years on the farm. Three county-based risk regions (RR) were identified by use of cluster analysis. RESULTS--Mean seroprevalence for each of the 3 RR was 2.4 (low risk), 8.5 (moderate risk), and 18.5% (high risk) for cohort 1 and 2.5, 8.0, and 18.4% for cohort 2. Among cohorts 1 and 2, pleasure riding and breeding trips were associated with exposure to E risticii, but horse residence (low, moderate, or high RR) was an effect modifier for these associations. Among cohort 1 and stratifying the analysis according to the RR for the travel destination, trail riding at low RR and trail riding at high RR were associated with exposure. Among cohort 2 and stratifying the analysis according to the RR for the travel destination, breeding trips were associated with exposure, and strong effect modification was present for horse residence (low, moderate, or high RR). CONCLUSIONS--Only certain types of travel to specific RR were associated with higher risk of exposure to E risticii. In many instances, travel was not associated, or was associated, with a reduced risk of exposure.
|
|
Bennett, A. T. (1996). Do animals have cognitive maps? J Exp Biol, 199(Pt 1), 219–224.
Abstract: Drawing on studies of humans, rodents, birds and arthropods, I show that 'cognitive maps' have been used to describe a wide variety of spatial concepts. There are, however, two main definitions. One, sensu Tolman, O'Keefe and Nadel, is that a cognitive map is a powerful memory of landmarks which allows novel short-cutting to occur. The other, sensu Gallistel, is that a cognitive map is any representation of space held by an animal. Other definitions with quite different meanings are also summarised. I argue that no animal has been conclusively shown to have a cognitive map, sensu Tolman, O'Keefe and Nadel, because simpler explanations of the crucial novel short-cutting results are invariably possible. Owing to the repeated inability of experimenters to eliminate these simpler explanations over at least 15 years, and the confusion caused by the numerous contradictory definitions of a cognitive map, I argue that the cognitive map is no longer a useful hypothesis for elucidating the spatial behaviour of animals and that use of the term should be avoided.
|