SEARCH BEHAVIOR OF DOGS (CANIS-FAMILIARIS) IN INVISIBLE DISPLACEMENT PROBLEMS

Gagnon and Dore (1992) showed that domestic dogs are able to solve a P iagetian object permanence task called the invisible displacement prob lem. A toy is hidden in a container which is moved behind a screen whe re the toy is removed and left. Dogs make more errors in these problem s than they do in visible displacement tests, in which the object is h idden directly behind the target screen. In Experiment 1, we examined components of the standard procedure of invisible displacements that m ay make encoding or retention of the hiding location more difficult th an it is in visible displacements. In Experiment 2, we compared dogs' performances in visible and invisible displacement problems when delay s of 0, 10, and 20 sec were introduced between the object's final disa ppearance and the subject's release. The results revealed that dogs' p oorer performance in invisible displacement tests is related to the co mplex sequence of events that have to be encoded or remembered as well as to a difficulty in representing the position change that is signal ed, but not directly perceived.