Abstract: Gagnon and Dor (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 examinedcomponents ofthe 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
objects final disappearance and the subjects 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.