Three degrees of severity of restriction were imposed on dogs for the first 7 to 10 months of life, litter-mate controls being raised as pets. All animals were later tested in a free exploration test and in a maze test. Results indicate: (1) exploratory activity decreases as a function of time of exposure, (2) restricted dogs explore more than normal animals, the more restricted exploring most; (3) younger dogs explore more than older dogs. (PsycINFO Database Record (c) 2006 APA, all rights reserved)