Biomedical subjects

Edward A Wasserman

Publications and source records attributed to Edward A Wasserman.

26 records · Page 2Linked to original sources

PubMed2003

Pigeons learn stimulus identity and stimulus relations when both serve as redundant, relevant cues during same-different discrimination training.

The authors taught pigeons to discriminate displays of 16 identical items from displays of 16 nonidentical items. Unlike most same-different discrimination studies--where only stimulus relations could serve a discriminative function--both the identity of the items and the relations among the items were discriminative features of the displays. The pigeons learned about both stimulus identity and stimulus relations when these 2 sources of information served as redundant, relevant cues. In tests of associative competition, identity cues exerted greater stimulus control than relational cues. These results suggest that the pigeon can respond to both specific stimuli and general relations in the environment.

Analysis of Variance↗

PubMed2002

Learning an object from multiple views enhances its recognition in an orthogonal rotational axis in pigeons.

In the natural environment, most objects are seen from several different viewpoints. We explored the nature of recognition after training with multiple views and compared it to recognition after training with only one view. Pigeons were taught with either five views or one view of each of four single-geon objects. Pigeons trained with five views responded more accurately to novel views of an object than did pigeons trained with only one view. This result held even when the novel views came from a rotational axis that was orthogonal to the training axis. These results do not accord with recognition processes involving mental rotation or direct interpolation. Pigeons trained with five views may have formed a view-invariant representation [Psychol. Rev. 94 (1987) 115; Vision Res. 39 (1999) 2885]; alternatively, they may have acquired a more detailed shape space of the objects in which to measure object similarity [Representation and recognition in vision, MIT Press, MA, 1999], or learned to attend to a broader range of features of each object [J. Exp. Anal. Behav. 54 (1990) 69].

Animals↗

PubMed2002

Detecting variety: what's so special about uniformity?

People and pigeons were taught to make 1 of 2 responses to 16-icon arrays that differed in their visual variability. In 2 experiments, participants had to (a) discriminate a collection of identical items from a collection in which 2 or more items were different or (b) discriminate a collection of different items from a collection in which 2 or more items were identical. In Experiment 1, humans found it much easier to discriminate uniformity from all levels of diversity. In Experiment 2, pigeons also found it easier to discriminate uniformity from all levels of diversity, but the size of this effect was smaller than that observed in people. These and other results suggest that both species are predisposed to notice differences rather than similarities.

Analysis of Variance↗

PubMed2002

Limited attention and cue order consistency affect predictive learning: a test of similarity measures.

The authors empirically tested the similarity metrics underlying 2 predictive-learning theories: J. K. Kruschke's (1992) attention learning covering map and J. M. Pearce's (1987, 1994) configural models. In Experiment 1, participants concurrently learned 3 types of discriminations: simple (A- vs. B+), common cue (XC- vs. XD+), and compound (YE- vs. ZF+). Accuracy was ordered: simple > compound > common cue. Neither model anticipated this ordering. In Experiment 2, cue order in 2-element configurations was either inconsistent (e.g., YE and EY) as in Experiment 1 or consistent (e.g., EY throughout). Although accuracy differences were smaller under consistent ordering, the relative difficulty of the tasks was the same as in Experiment 1. In Experiment 3, common cue and compound discriminations were tested in different participants to determine whether the ordering of difficulty in Experiments 1 and 2 was caused by differential generalization mediated by the number of elements; the ordering was the same as in Experiments 1 and 2. These results suggest the need for differential attention to event presence and absence and to mechanisms that incorporate limited attentional capacity.

Analysis of Variance↗

PubMed2002

Effects of occlusion on pigeons' visual object recognition.

Casual observation suggests that pigeons and other animals can recognize occluded objects; yet laboratory research has thus far failed to show that pigeons can do so. In a series of experiments, we investigated pigeons' ability to 'name' shaded, textured stimuli by associating each with a different response. After first learning to recognize four unoccluded objects, pigeons had to recognize the objects when they were partially occluded by another surface or when they were placed on top of another surface; in each case, recognition was weak. Following training with the unoccluded stimuli and with the stimuli placed on top of the occluder, pigeons' recognition of occluded objects dramatically improved. Pigeons' improved recognition of occluded objects was not limited to the trained objects but transferred to novel objects as well. Evidently, the recognition of occluded objects requires pigeons to learn to discriminate the object from the occluder; once this discrimination is mastered, occluded objects can be better recognized.

Animals↗

PubMed2002

Brief presentations are sufficient for pigeons to discriminate arrays of same and different stimuli.

Four pigeons first learned to discriminate 16-item arrays of same from different pictorial stimuli. They were then tested with reduced exposure to the pictorial arrays, brought about by changes in the stimulus viewing requirement under fixed-ratio (FR) and fixed-interval (FI) schedules. Increasing the FR requirement enhanced discriminative performance up to 10 pecks; increasing the FI requirement enhanced discriminative performance up to 5 s. Exposures to the stimulus arrays averaging only 2 s supported reliable discrimination. Pigeons thus discriminate same from different stimuli with considerable speed, suggesting that same-different discrimination behavior is of substantial adaptive significance.

Animals↗

PubMed2002

The pigeon's discrimination of visual entropy: a logarithmic function.

We taught 8 pigeons to discriminate 16-icon arrays that differed in their visual variability or "entropy" to see whether the relationship between entropy and discriminative behavior is linear (in which equivalent differences in entropy should produce equivalent changes in behavior) or logarithmic (in which higher entropy values should be less discriminable from one another than lower entropy values). Pigeons received a go/no-go task in which the lower entropy arrays were reinforced for one group and the higher entropy arrays were reinforced for a second group. The superior discrimination of the second group was predicted by a theoretical analysis in which excitatory and inhibitory stimulus generalization gradients fall along a logarithmic, but not a linear scale. Reanalysis of previously published data also yielded results consistent with a logarithmic relationship between entropy and discriminative behavior.

Animals↗

PubMed2002

Stimulus control by same-versus-different relations among multiple visual stimuli.

The authors devised a go/no-go discrimination learning task that allowed but did not require pigeons to report (a) from which of 2 different sets a collection of visual items was drawn and (b) the relations between or among the items as being the same as or different from one another. The results of 2 experiments using this task disclosed stimulus control by the particular items in the arrays and by the same-different relations exemplified by those items. Relational and item control depended on how many items were in the arrays. Same-different discrimination was evident with 2-item displays, but it was much stronger with 6 or more items. These findings help to define the substrates of advanced conceptual behavior.

Analysis of Variance↗