Marcus, Nolen, Rankin, and Carew (1988) conducted a series of experiments to address the debate over the dual-process view of nonassociative learning. The dual-process view of nonassociative learning relies on the relationship between a decreasing process producing habituation and an increasing process that allows dishabituation and sensitization to occur. Habituation is a decrease in response due to repeated stimulation. On the other hand, sensitization is an increase in response due to repeated stimulation. Dishabituation is the elicitation of a habituated response after a dishabituating stimulus is presented. Marcus et al. (1988) developed the multiprocess view of nonassociative learning as an alternative to the dual-process view. Using the Aplysia, Marcus et al. (1988) concluded that dishabituation and sensitization are different behaviorally and that a multiprocess view must be adopted. The multiprocess view takes into consideration the various mechanisms behind nonassociative learning.
The first set of experiments examined dishabituation. Marcus et al. (1988) produced habituation by administering a series of 20 water-jet stimuli to the siphon of the Aplysia. They then gave a single stimulus to the tail of the Aplysia. To evaluate the onset of dishabituation, the experimenters used two groups, one group receiving the tail stimulus and the other group receiving no tail stimulus after habituation. The group receiving no tail stimulus was classified as the recovery group while the group receiving the stimulus was labeled the dishabituation group. The stimulus was given 90 seconds, ten minutes, and 20 minutes after the water-jet stimuli. The dishabituation group responded with greater magnitude after 90 seconds. Both the dishabituation and recovery groups exhibited a response magnitude after ten and 20 minutes, so the rest of the experiment was restricted to the 90-second test. Marcus et al. (1988) did this to be certain response magnitude was a result of dishabituation and not recovery. It was concluded that dishabituation has an early onset. The experimenters also varied the intensity of the stimulus given to the tail. The weaker the tail stimuli, the greater the magnitude of dishabituation observed.
The second set of experiments focused on sensitization. The same process used for
dishabituation was used to asses sensitization, but this group was only presented with two baseline stimuli to...