Studies of individual differences as a method for discriminating the stages of acquisition of a conditioned reflex.

Learning of a two-way active avoidance response in a shuttle box, which reflects the establishment of a complex reflex, was characterized by a high level of individual variability for learning measures. Our previous report (Savonenko and Zelin'ski, 1997) showed that rats with different rates of learning have different parameters for the freezing response, demonstrating that the animals' behavior shows a conflicting drive not to enter into the other half of the box. We analyze here the sequence of freezing, avoidance, and escape responses in groups of rats with different rates of learning. The results support the hypothesis that the need to overcome conflict is a separate stage of learning, occurring before the stage at which the avoidance response forms and stabilizes.