Sex differences, context preexposure, and the immediate shock deficit in Pavlovian context conditioning with mice

The acquisition of context fear in rats is affected by variables such as th e sex of the animal, the placement to shock interval (PSI), and preexposure to the context. The current experiments assessed the effects of these vari ables on context conditioning in mice (C57BL/6). In Experiment 1, mice were placed in a chamber and received a single shock 5 s, 20 s, 40 s, 60 s, 180 s, or 720 s later. Increasing the PSI produced corresponding increases in conditional freezing during the context test. In addition, male mice acquir ed more context conditioning than female mice did but only at intermediate PSIs. In Experiment 2, preexposure to the context before training alleviate d the sex difference found with an intermediate PSI. The results are discus sed in terms of configural learning theory and are argued to be contrary to the predictions of scalar expectancy theory.