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| International Paper Session - Stimulus Control I |
| Sunday, May 27, 2007 |
| 10:00 AM–11:20 AM |
| Madeleine CD |
| Area: EAB |
| Chair: Dennis J. Hand (Central Michigan University) |
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| Does Peak Shift Occur in the Natural Environment? Evidence from Judgments of Human Faces and Women’s Torsos. |
| Domain: Basic Research |
| ADAM DERENNE (University of North Dakota), Karla Fehr (University of North Dakota), R. Michael Breitstein (University of North Dakota) |
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| Abstract: ”Peak shift” describes a displacement in a generalization gradient away from a negative exemplar shown during training and towards extreme values on the opposite end of the stimulus dimension. Peak shift is best known from research with humans and nonhumans involving judgments of simple, unidimensional stimuli. To examine whether peak shift can plausibly affect judgments in the natural environment, the stimulus dimension in two experiments consisted of either human faces or women’s torsos. In one experiment, participants were trained to discriminate human faces on the basis of the proportion of the total face length that was below the nose. In a second experiment, participants were trained to discriminate among images of women’s torsos on the basis of the relative waist-to-hip ratio. In both cases, peak shift was obtained. The discussion focuses on contemporary theories of peak shift and the possible role of the underlying processes in naturally occurring perceptual distortions. |
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| Automated Equipment for Simple Two-Choice Olfactory and Tactile Discrimination in Rats. |
| Domain: Basic Research |
| IVER H. IVERSEN (University of North Florida) |
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| Abstract: Research with rats rarely explores sensory modalities other than vision and hearing. The present research used a horizontal disk attached to a bidirectional motor to present stimuli for olfactory or tactile discrimination. Two adjacent disk quarters were occupied with identical stimuli, such as sandpaper of a given grade for tactile discrimination. Thus, two different grades of sandpaper could be placed on the disk. The rat palpitated one quarter of the disk through a slot in the wall and then selected one of two levers to indicate which stimulus (rough or smooth) was on the disk. A PC computer controlled disk rotation (one step left or right) during the inter-trial interval to present the same or the different stimulus on the next trial. Similarly for olfactory discrimination, two odorous stimuli (such as two types of tea bags) were placed on the disk; the rats would sniff at the stimulus through a perforated slot in the wall. Using a food-reinforcement paradigm, rats learned these discriminations (in total darkness to avoid visual cues) at a near 100% accuracy within a few weeks of daily training in sessions with 100 trials. The equipment is useful for experiments that examine simple cross-modal discriminations in rats. |
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| Identifying Multiple Stimulus Control Topographies in the Identity Matching Performance in a Capuchin Monkey. |
| Domain: Basic Research |
| ROMARIZ BARROS (Universidade Federal do Para), Paulo R. K. Goulart (Universidade Federal do Para), Carlos Rafael P. Diniz (Universidade Federal do Para), Olavo Galvao (Universidade Federal do Para) |
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| Abstract: Generalized identity matching is sometimes hard to find in non-human subjects or people with severe developmental disabilities. Our laboratory is dedicated to study procedural variables in the development of complex stimulus control in capuchin monkeys. Our standard procedure has been successful to produce generalized identity matching in most of our monkeys. This presentation reports a case of failure of our standard procedure to produce generalized identity matching. The standard procedure comprised several steps beginning with a touch screen response shaping procedure, followed by simple discrimination reversal training, identity matching and tests for generalized identity matching. The data obtained with the particular subject here reported showed high accuracy in the directly trained identity matching task but consistent failure to perform the same task with new stimuli. Procedures to reduce inappropriate response topographies and encourage stimulus control coherence were introduced. Then, identity matching tests Type 1 (whole new stimulus set) versus Type 2 (new S+ plus a few known S-) produced respectively intermediate and high accuracies. Ultimately, two different stimulus control tests were successfully carried out to identify one interfering stimulus control topography. The behavioral intervention here presented may be useful to inspire research and intervention to people with severe developmental disabilities. |
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