[MARMAM] Invisible Displacement in Dolphins

c8johnson at ucsd.edu c8johnson at ucsd.edu
Thu Aug 21 18:58:07 PDT 2014

Dear colleagues,

Greetings! We are delighted to announce a new paper on dolphin cognition -

Johnson, C.M., Sullivan, J., Buck, C.L., Trexel, J. & Scarpuzzi, M. (2014)
Visible and invisible displacement with dynamic visual occlusion in
bottlenose dolphins (Tursiops spp) ANIMAL COGNITION, 18.
DOI 10.1007/s10071-014-0788-2



Anticipating the location of a temporarily obscured target - what Piaget
(1954) called "object permanence" - is a critical skill, especially in
hunters of mobile prey. Previous research with bottlenose dolphins found
they could predict the location of a target that had been visibly
displaced into an opaque container, but not one that was first placed in
an opaque container and then invisibly displaced to another container. We
tested whether, by altering the task to involve occlusion rather than
containment, these animals could show more advanced object permanence
skills. We projected dynamic visual displays at an underwater-viewing
window and videotaped the animals' head moves while observing these
displays. In Experiment 1, the animals observed a small black disk moving
behind occluders that shifted in size, ultimately forming one large
occluder. Nine out of ten subjects "tracked" the presumed movement of the
disk behind this occluder on their first trial --  and in a statistically
significant number of subsequent trials -- confirming their visible
displacement abilities. In Experiment 2, we tested their invisble
displacement abilities. The disk first disappeared behind a pair of moving
occluders, which then moved behind a stationary occluder. The moving
occluders then reappeared and separated, revealing that the disk was no
longer behind them. The subjects subsequently looked to the correct
stationary occluder on 8 of their 10 first trials, and in a statistically
significant number of subsequent trials. Thus, by altering the stimuli to
be more ecologically valid, we were able to show that the dolphins could
indeed succeed at an invisible displacement task.

Keywords:   Object permanence, invisible displacement, bottlenose
dolphins, occlusion, secondary representations

Rerints available on request.

Chris Johnson et al

Christine M. Johnson, PhD
Department of Cognitive Science
University of California, San Diego
Ph: 858-534-9854
FAX  858-534-1128

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