LEARNING IN THE SPINY LOBSTER PANULIRUS ARGUS

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1. Juvenile spiny lobsters (Panulirus argus) could be trained in air in a two-choice discrimination box to use two stimulating lights which differed in intensity by a factor of 3-5 times in learning to reach an open exit hole leading to an aquarium containing sea water.2. Comparable training procedures yielded no better than chance selection of the two compartments (one with the open exit, the other with its exit blocked) when the conditioning lights were of equal intensity but were both linearly polarized, one horizontally, the other vertically. Demonstration that lobsters did not use polarization pattern in this spatial discrimination situation does not prove that the plane of polarization was not perceived by Panulirus.3. Learning was more rapid than it was to intensity differences when the animals were trained always to go to one side of the discrimination box to reach the open exit. For intensity discrimination initial high percentage errors were reduced to less than 20% only on the twentieth day after 104 trials per animal, whereas for training to side less than 20% errors were achieved after 20 trials per animal.4. Learning indicated by the curve of mean error scores per day resembles an exponential decay function and is accompanied by decreases in percentage of nonspontaneous runs and runs showing tail-flexing movements. Tail-flexing movements were correlated positively with error runs and occurred as a result of "indecisive" behavior.5. Learning indicated by reduction in percentages of nonspontaneous runs showed retention of training between experiments and continued in cases where exit discrimination was not being learned. Hence over-all training involved: (a) learning to walk directly forward, and (b) learning to discriminate the side with the open exit.