Laboratory rats have also proved valuable in psychological studies of learning and other mental processes -LRB- PERSON@1 , NUMBER@1 -RRB- , as well as to understand group behavior and overcrowding -LRB- with the work of PERSON@2 on behavioral sink -RRB- .

Laboratory rats have also proved valuable in psychological studies of learning and other mental processes -LRB- PERSON@1 , NUMBER@1 -RRB- .
