This study investigated the effects of inescapable shock on subsequent escape/avoidance learning in dogs. Dogs that had learned to escape shock in a harness showed normal escape behavior in a shuttle box. However, dogs that experienced inescapable shock in the harness showed profound interference with subsequent escape responding in the shuttle box. Initial experience with escape in the shuttle box enhanced panel pressing during inescapable shock in the harness and prevented interference with later responding in the shuttle box. Inescapable shock in the harness and failure to escape in the shuttle box produced interference with escape responding after a 7-day rest. These results supported the learned "helplessness" explanation of interference with escape responding: dogs failed to escape shock in the shuttle box following inescapable shock in the harness because they had learned that shock termination was independent of responding. Experiment I showed that dogs that learned to escape shock in the harness did not differ from untreated dogs in subsequent escape/avoidance learning in the shuttle box. Dogs for which shock termination was independent of responding in the harness showed interference with subsequent escape learning. The results suggested that differential learning about control over shock occurred in these two groups. The "Yoked" control group, which learned that shock termination was independent of responding, showed interference with escape responding in the shuttle box. In contrast, the Escape group, which learned that their responding was correlated with shock termination, did not show interference. Experiment II investigated whether prior experience with escapable shock in the shuttle box would mitigate the effects of inescapable shock in the harness on subsequent escape/avoidance behavior. The results showed that dogs that first received escapable shock in the shuttle box did not react passively to subsequent shock in the shuttle box, unlike dogs that had received inescapable shock in the shuttle box or no treatment prior to shock in the harness. The Preescape group showed enhanced panel pressing when exposed to inescapable shock in the harness, relative to naive dogs given inescapable shock in the harness. This enhanced panel pressing was specifically the result of the escapability of shock in the shuttle box. The interference effect persisted for 40 trials. The study supports the concept of learned helplessness, where animals learn that their responses do not affect shock termination, leading to passive acceptance of shock. The results suggest that learning about the relationship between responding and shock termination plays a crucial role in escape/avoidance behavior. The findings have implications for understanding how animals learn to avoid or escape aversive stimuli and how this learning can be affected by prior experiences.This study investigated the effects of inescapable shock on subsequent escape/avoidance learning in dogs. Dogs that had learned to escape shock in a harness showed normal escape behavior in a shuttle box. However, dogs that experienced inescapable shock in the harness showed profound interference with subsequent escape responding in the shuttle box. Initial experience with escape in the shuttle box enhanced panel pressing during inescapable shock in the harness and prevented interference with later responding in the shuttle box. Inescapable shock in the harness and failure to escape in the shuttle box produced interference with escape responding after a 7-day rest. These results supported the learned "helplessness" explanation of interference with escape responding: dogs failed to escape shock in the shuttle box following inescapable shock in the harness because they had learned that shock termination was independent of responding. Experiment I showed that dogs that learned to escape shock in the harness did not differ from untreated dogs in subsequent escape/avoidance learning in the shuttle box. Dogs for which shock termination was independent of responding in the harness showed interference with subsequent escape learning. The results suggested that differential learning about control over shock occurred in these two groups. The "Yoked" control group, which learned that shock termination was independent of responding, showed interference with escape responding in the shuttle box. In contrast, the Escape group, which learned that their responding was correlated with shock termination, did not show interference. Experiment II investigated whether prior experience with escapable shock in the shuttle box would mitigate the effects of inescapable shock in the harness on subsequent escape/avoidance behavior. The results showed that dogs that first received escapable shock in the shuttle box did not react passively to subsequent shock in the shuttle box, unlike dogs that had received inescapable shock in the shuttle box or no treatment prior to shock in the harness. The Preescape group showed enhanced panel pressing when exposed to inescapable shock in the harness, relative to naive dogs given inescapable shock in the harness. This enhanced panel pressing was specifically the result of the escapability of shock in the shuttle box. The interference effect persisted for 40 trials. The study supports the concept of learned helplessness, where animals learn that their responses do not affect shock termination, leading to passive acceptance of shock. The results suggest that learning about the relationship between responding and shock termination plays a crucial role in escape/avoidance behavior. The findings have implications for understanding how animals learn to avoid or escape aversive stimuli and how this learning can be affected by prior experiences.