400
The experiment involved using rats and separating them either to an enriched environment (a cage with toys) or a deprived environment (a cage without toys). The rats in the deprived environment had individual cages as well so lacked communication with other rats. The rats were kept in the cages for 30-60 days for the experiment before results were conducted.
Rosenzweig and Bennet (1972) conducted a study on brain plasticity. What was the method they used in their research?