One form of learning used in these studies was classical conditioning. A light touch to Aplysia’s siphon causes the animal to withdraw its gill slightly (fig. 4.3). When a light touch to the siphon is followed immediately by a shock to Aplysia’s tail, the animal learns that the touch to the siphon predicts the shock to the tail. A subsequent light touch to the siphon alone will produce a massive withdrawal of the gill. Thus, in classical conditioning Aplysia learns to associate the light touch to the siphon with the shock that follows it.
