The what and the where of the pigeon's processing of complex visual stimuli (original) (raw)

The pigeon’s performance on shape and location discriminations

Visual Cognition

Two groups of pigeons (n = 4) were trained with 16 line drawings portraying a fixed shape and a variable shape. The four variable shapes (a wedge, a cone, a cylinder, and a handle) appeared to the left of, to the right of, above, or below the fixed shape (a cube). Group Shape (S) was required to discriminate the identity of the variable shape that was mated with the cube, whereas Group Location (L) was required to discriminate where the variable shape appeared relative to the cube. Three of the four pigeons in each group mastered their respective tasks. Later tests revealed that the two groups of pigeons had attended to different aspects of the shape pairs, even though the visual stimuli and general procedures they had been given were the same. Group S had attended to the identity of the variable shape and had ignored the identity and location of the cube, whereas Group L had attended to the configuration of the two shapes. The methods and stimuli could be useful in delineating the biological bases of shape and location perception.

The pigeon's discrimination of shape and location information

2000

Pigeons are sensitive to the spatial organization of complex visual stimuli

1993

Abstract Two experiments investigated the role of spatial organization in the discrimination and generalization of complex visual stimuli by pigeons. In Experiment 1. after pigeons had been trained to discriminate line drawings of four objects, they were tested with novel pictures in which the same component parts of the objects were spatially rearranged. The spatially scrambled pictures led to a dramatic drop in recognition accuracy, but responding remained above chance.

Stimulus display geometry and colour discrimination learning by pigeons

Current Psychological Research, 1981

Pigeons learned a successive conditional visual discrimination on vertically and horizontally arranged pairs of stimulus-response keys. When the discriminanda were two similar hues the pigeons' performance was significantly better on the vertical than on the horizontal task. This was also found in an experiment in which the subjects could see only monocularly. When, however, the discriminative stimuli were patterns of different orientation or markedly dissimilar hues then the performance on the horizontal task had an advantage over that on the vertical one. A horizontal advantage also obtained when si milar hues were discriminated on keys clustered closely together. Pigeons thus seem more adept at solving successive conditional dis cr irnl nations on horizontal than on vertical pairs of keys except when similar hues are displayed on widely separated keys where the reverse is true. It is hypothesized that colour vi s i o n inequalities due to regional retinal differentiations are responsible for this latter effect.

Object discrimination in pigeons: Effects of local and global cues

Vision Research, 2006

We trained two pigeons to report whether a pair of diVerently colored 2-D objects had two target dots on either one or both of the objects. Follow-up tests disclosed that the colored regions surrounding the task-relevant targets were necessary, but not suYcient to support the birds' discrimination. Moreover, when local and global color cues provided contradictory information, pigeons failed to discriminate the stimuli, suggesting that the birds attended to both local and global information. Finally, one bird learned the object discrimination in the absence of diVerential color cues suggesting that, with suitable training, pigeon can attend to entire objects. 

Context effects in visual pattern recognition by pigeons

Perception & Psychophysics, 1994

In the experiments described in this paper we examined the effects of contextual stimuli on pigeons' recognition of visual patterns. Experiment 1 showed a context-superiority effect. Specifically, two target forms that were identical except for location in the visual field were not discriminated when presented alone, but the compounds formed when each of these targets was placed between a nearby pair of flanking stimuli were readily discriminated. The size of the contextsuperiority effect decreased with increasing target-flanker separation. In Experiments 2 and 3 the two targets differed in form rather than spatial location and were readily discriminated in the absence of flankers. Under these circumstances, adding an identical pair of flankers to each target resulted in a context-inferiority effect; that is, the two target-plus-flankers compounds were less readily discriminated than the targets alone. The size of the context-inferiority effect decreased with increasing target-flanker separation. The observed effects of context are predictable from the Heinemann-Chase (1990) model of pattern recognition.

Stagewise Multidimensional Visual Discrimination by Pigeons

We trained six pigeons in a stagewise Multiple Necessary Cues (MNC) go/no-go task to document the dynamics of discrimination learning involving increasingly complex visual stimuli. The compound stimuli were composed from four dimensions, each of which could assume either of two extreme values or their intermediate value: Shape, Size, Line Orientation, and Brightness. Starting with a stimulus composed entirely from intermediate values, we replaced those values with each of the two extreme dimensional values in four successive stages, thereby increasing the stimulus set from 2 in Stage 1 to 16 in Stage 4. In each stage, only one combination of values signaled food (S +), whereas the remaining combinations did not (S − s). We calculated the rate of pecking during the first 15 s of each stimulus presentation and, in any given stage, training continued until the rate of responding to all of the S − s was less than 20% of the rate of responding to the S +. All pigeons successfully acquired the final discrimination, suggesting that they attended to all of the dimensions relevant for the discrimination. We also repli-cated the key results of prior MNC studies: (1) the number of extreme dimensional values in each stage was positively related to the amount of training required for pigeons to acquire the discrimination; (2) attentional tradeoffs were most often observed when three or four dimensions were being trained; and (3) throughout training, the number of dimensional values in the S − s that differed from the S + was positively related to their discriminability from S + .

Selective attention and pigeons' multiple necessary cues discrimination learning

Behavioural processes, 2015

We deployed the Multiple Necessary Cues (MNC) discrimination task to see if pigeons can simultaneously attend to four different dimensions of complex visual stimuli. Specifically, we trained eight pigeons on a simultaneous discrimination to peck only 1 of 16 compound stimuli created from all possible combinations of two stimulus values from four separable visual dimensions: shape (circle/square), size (large/small), line orientation (horizontal/vertical), and brightness (dark/light). Some pigeons had CLHD (circle, large, horizontal, dark) as the positive stimulus (S+), whereas others had SSVL (square, small, vertical, light) as the S+. All eight pigeons acquired the MNC discrimination, suggesting that they had attended to all four dimensions. Learning rate was similar to all four dimensions, with learning along the orientation dimension being a bit faster than along the other three dimensions. The more dimensions along which the S-s differed from the S+, the faster was learning, sug...

Location as a feature in pigeons' recognition of visual objects

Journal of experimental psychology. Animal learning and cognition, 2022

A number of different phenomena in pigeon visual cognition suggest that pigeons do not immediately recognize two identical objects in different locations as being "the same." To examine this question directly, pigeons were trained in an absolute go/no-go discrimination between arbitrary selections from sets of 16 images of paintings by Claude Monet. Of the eight positive stimuli, four always appeared in the same location, whereas the other four appeared equally often in each of two locations; the same was true of the negative stimuli. There was a consistent tendency for stimuli that appeared in a single position to be better discriminated than those that appeared in two positions, although by the end of training this effect was confined to negative stimuli. This result suggests that, for a pigeon, an image's location is one of the bundle of features that define it, and that pigeons need to learn to abstract from that feature rather than doing so automatically. (PsycInf...

Effects of stimulus manipulations on visual categorization in pigeons

Behavioural Processes, 2006

Four pigeons were previously trained . Pigeons concurrently categorize photographs at both basic and superordinate levels. Psychon. Bull. Rev. 11, 1111-1117 to classify color photographs into either their proper basic-level category (cars, chairs, flowers, or people) or a superordinate-level category (nominally natural or artificial). In Experiment 1, the same pigeons were shown either reflected or inverted versions of the training stimuli. Reflection had no effect on pigeons' classification behavior, whereas inversion impaired discrimination of all stimulus categories, except flowers, on the basic-level and superordinate-level tasks. Pixel matching analysis revealed that pattern matching played at most a minor role in the birds' categorization behavior. In Experiment 2, the pigeons were shown test stimuli that were either blurred or quartered and scrambled. Blurring impaired discrimination of cars, but had no effect on discrimination of people and flowers; scrambling impaired discrimination of people and flowers leaving discrimination of cars and chairs unaffected. These results suggest that categorization of flowers and people may be controlled primarily by the overall shape of the object rather than by local features, whereas categorization of cars and chairs may rely primarily on local features rather than the overall shape of the object.

The what and the where of the pigeon's processing of complex visual stimuli (original) (raw)

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