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

Gagnon and Dore (1992) showed that domestic dogs are able to solve a Piagetian object permanence task called the invisible displacement problem. A toy is hidden in a container which is moved behind a screen where the toy is removed and left. Dogs make more errors in these problems than they do in visible displacement tests, in which the object is hidden directly behind the target screen. In Experiment 1, we examined components of the standard procedure of invisible displacements that may make encoding or retention of the hiding location more difficult than it is in visible displacements. In Experiment 2, we compared dogs' performances in visible and invisible displacement problems when delays of 0, 10, and 20 sec were introduced between the object's final disappearance and the subject's release. The results revealed that dogs' poorer performance in invisible displacement tests is related to the complex sequence of events that have to be encoded or remembered as well as to a difficulty in representing the position change that is signaled, but not directly perceived.