Bar orientation in operant escape training

In operant escape training a rat is usually required to deflect a bar in a downward direction to terminate shock for a short interval of time. In the study described here, eight rats were conditioned with the bar mechanism modified to require a sideways deflection. The acquisition of escape responding with the bar in the modified position was inferior to the responding typically observed with the bar in the usual position. Sequences of successful escape responding were observed when the bar required a sideways deflection, but the response-reinforcement contingency was not adequate to maintain escape behavior.