Lever-press conditioning in the crab.
An operant chamber has been developed for studying lever-press conditioning in the green crab Carcinus maenas. In one series of experiments, animals were presented with a single bar and were reinforced with food for every bar press. Performance increased over time and high rates of responding were observed after 2 days of training. The response rate was always higher than that for a yoked (noncontingent) control group. When the contingencies were switched, the animals adjusted to the new conditions. Discrimination in the lever-press apparatus was demonstrated in a second experiment in which crabs had to choose between two bars, one (S+) caused food to be dispensed while the other (S-) was inactive. Experimental animals pressed the S+ bar at a significantly higher rate than the S- bar. When the contingencies associated with the lever were reversed, animals learned to switch to the correct bar by the second day. It was not necessary to reinforce every response: animals maintained high rates of responding on a schedule where every other response was reinforced. Animals used different methods of pressing the bar; the most common was extension of the claw, predominantly at the meropodite-carpopodite joint.
Abramson
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Department of Biochemistry, State University of New York Health Science Center, Brooklyn 11203.
Feinman
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D000818:Animals; D001070:Appetitive Behavior; D001245:Association Learning; D003386:Brachyura; D003216:Conditioning, Operant; D004193:Discrimination Learning; D009042:Motivation; D011597:Psychomotor Performance; D012055:Reinforcement Schedule