Pigeon perception and discrimination of rapidly changing texture stimuli

The perception and discrimination of rapidly changing texture stimuli by pigeons was examined in a target localization task. Five experienced pigeons were rewarded for finding and pecking at a randomly placed odd target block of small repeated elements embedded in a larger rectangular array of contrasting distractor elements. On dynamic color test trials, the color of the target, distractor, or both of these regions changed at rates of 100, 250, 500, or 1000 ms per frame. The number of colors appearing within such trials also varied. Pigeons performed well above chance in all test conditions, with target-associated changes producing the best discrimination. The results suggest: (a) global relational information can exclusively guide target localization behavior, (b) pigeons can perceptually group and segregate colored textured differences quite rapidly (< or = 100 ms), and (c) pigeons may possess automatic search control processes that can be captured by stimulus-driven changes in the display.     

Tardive dyskinesia in a developmentally disabled population: Manifestation during the initial stage of a minimal effective dose program.

Forty individuals who were withdrawn from neuroleptic medication after the initiation of a minimal effective dose program at a residential facility for individuals with developmental disabilities were evaluated. Tardive dyskinesia (TD) was assessed using the Dyskinesia Identification System Condensed User Scale (DISCUS). Half of the participants being treated with neuroleptic medication (N) were also being treated with anticonvulsant medication (AC), so 2 withdrawal groups were formed. The N only group manifested an increase in DISCUS scores after the withdrawal of neuroleptic medication, but the N?+?AC group did not. On the basis of this intriguing new finding, it was speculated that treatment with anticonvulsant medication might prevent the development or suppress the expression of TD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeon same–different concept learning with multiple stimulus classes.

Two experiments examined the acquisition and transfer of a complex same–different discrimination by pigeons. With the use of a 2-alternative choice task, 5 pigeons were reinforced for discriminating odd-item Different displays, in which a contrasting target was present, from Same displays, in which all elements were identical. Four different types of same-different displays were concurrently tested. The display types differed in their configuration (texture vs. visual search organization), the nature of their elements (small and large colored shapes; pictures of birds, flowers, fish, and humans), and the processing demands required by their global-local element arrangement. Despite these differences, the pigeons learned to discriminate all 4 display types at the same rate and showed positive discrimination transfer to novel examples of each type, suggesting that a single generalized rule was used to discriminate all display types. These results provide some of the strongest evidence yet that pigeons, like many primates, can learn an abstract, visually mediated same-different concept. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive precedence for local information in hierarchical stimulus processing by pigeons.

Four experiments investigated the processing of hierarchical stimuli by pigeons. Using a 4 alternative divided–attention task, 4 pigeons were food-reinforced for accurately identifying letters arranged as either hierarchical global- or local-relevant stimuli or as size-matched filled stimuli. Experiment 1 found that task acquisition was faster with local-relevant than global-relevant stimuli. This difference was not due to letter size. Experiment 2 demonstrated successful transfer to a novel irrelevant letter configuration. Experiments 3 and 4 tested pigeons' responses to conflict probe stimuli composed of equally discriminable relevant letters at each level. These tests revealed that all of the pigeons showed a cognitive precedence for local information early in processing, with the pigeons using different cues to initiate the processing of global information. This local advantage contrasts with previously reported results for humans and pigeons but is similar to that reported for nonhuman primates. Alternatives attempting to reconcile these contrasting comparative results are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Same-different texture discrimination and concept learning by pigeons.

Investigated the acquisition and transfer of a "same-different" conditional discrimination using multidimensional visual texture stimuli in pigeons. Using a choice task, 4 pigeons were reinforced for discriminating different displays, created from aggregated differences in element color or shape, from uniform displays, in which all elements were identical. Discrimination of these 2 display types was readily acquired by the pigeons when they were required to locate and peck the contrasting target region of the different displays. The pigeons showed high levels of discrimination transfer to novel texture stimuli both during acquisition and in 2 subsequent transfer tests. The results suggest that pigeons may be able to learn a generalized same-different concept when promoted by the use of large numbers of multielement stimuli during training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)