Lever-press conditioning in the crab

Physiol Behav. 1990 Aug;48(2):267-72. doi: 10.1016/0031-9384(90)90311-q.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Appetitive Behavior*
  • Association Learning*
  • Brachyura*
  • Conditioning, Operant*
  • Discrimination Learning
  • Motivation
  • Psychomotor Performance*
  • Reinforcement Schedule