Duck Duck Choose: Ducklings Have 2 Separate Memory Banks of Visual Information

In a new study, published in the journal Animal Behaviour, scientists from the University of Oxford discovered that when a duck gathers visual information with one eye, that short-term information is not available when the other eye controls behavior. How did they find out? By observing how newly hatched ducklings that are shown a substitute mother object with only one eye do not recognize it when they have only the other eye available.

Antone Martinho, the study's first author and a research fellow in Oxford's Department of Zoology, stated: "When a bird sees something with both eyes simultaneously, each memory bank can acquire the same new information, and so the duck can act as though the two brain halves are informed."

Ducklings typically "imprint" on their mothers to learn to identify moving objects presented to it during its 'sensitive' period. In the study, Martinho presented the ducklings with either a red or a blue duck decoy, which moved in a circular path, while wearing an eye patch over one eye. The ducklings 'imprinted' on this maternal surrogate, learning with this first eye to follow the colored decoy they had been presented with.

Over the next three hours, each duckling was presented with both the red and blue decoys simultaneously while wearing either no eye patch, a patch over the same eye as in training, or a patch over the other eye or the one that had seen the decoy during training. The ducklings that made their choice with both eyes, or with the same eye with which they had been trained, accurately followed the original decoy. But the ducklings wearing a patch over the original eye, so that only the naive eye was available during testing, showed no reliable preference between the two decoys.

In most mammals, there is a large bridge connecting the two halves of the brain called the corpus callosum that allows rapid transfer of information between the two brain hemispheres. In birds, however, direct inputs from each eye go to the opposite side of the brain. This could mean information from one eye isn't readily available to the other.

These two competing banks of information could actually cause internal conflicts. Further testing showed that contradicting left and right imprints would neutralize each other.

"Most birds live a fast-paced life. Many are primarily prey animals needing to respond to a sighted predator at a moment's notice, all while each eye is sending different images to the brain," shared Martinho. "Furthermore, most birds fly. It is somewhat baffling to think that a flying bird may be acting in such a coordinated manner with two separate banks of information in its brain vying for behavioral control."