Human analog tests of object permanence were administered to various breeds of adult dogs (Canis familiaris). Experiment 1 showed that the performance of terriers, sporting, and working dogs did not differ. Dogs succeeded in solving invisible displacement problems, but performance was lower than in visible displacement tests. Familiarity with the task had some influence because invisible displacement tests were more successful if they were preceded by visible displacement tests. In Experiment 2, odor cues from the target object and the hiding screens were available or were masked. Results confirmed that success was lower in invisible than in visible displacement tests and that these problems were solved on the basis of representation of visual information rather than on the basis of olfactory cues or of local rule learning. Dogs are compared with other species that display Stage 6 object permanence.

Cats' and dogs' search behavior was compared in different problems where an object was visibly moved behind a screen that was then visiblymoved to a new position. In Experiments 1 (cats) and 2 (dogs), one group was tested with identical screens and the other group was tested with dissimilar screens. Results showed that in both species, search behavior was based on processing of spatial information rather than on recognition of the visual features of the target screen. Cats and dogs were unable to find the object by inferring its invisible movement. They reached a high level of success only if there was direct perceptual evidence that the object could not be at its initial position. When the position change was indicated by an indirect cue, cats searched more at the object's initial than [mal position, whereas dogs searched equally at both positions. Interspecific similarities and differences are interpreted in terms of the requirements for resetting working memory.

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