Learning of leg position by cockroaches in response to light.

Learning by the cockroach Periplaneta americana was studied using an electronic device that turns off a light in response to leg position. Training and testing were modeled on the Horridge procedure, with the position of a leg of one cockroach (P) controlling stimulation of both itself and a yoked control (R) during training, and the legs of P and R controlling stimulation independently during testing. In addition, testing was followed by reversal, in which each cockroach had to avoid the trained position in order to prevent exposure to light. During half-hour training periods. P cockroaches learned to lift a mesothoracic leg to turn off light. This learning was most evident during reversal, when P cockroaches continued to keep the leg lifted and were therefore exposed to appreciably more light than were R cockroaches. Cockroaches were unable to learn to lower the mesothoracic leg to escape light with a similar procedure.