Chicks: (4 or 5 days old), which art: able to use either eye freely, use th
e right eye (RE) preferentially in approach to a food dish when a lid, whic
h has to he removed, is visible during approach. They use the left eye (LE)
instead when no manipulation is required, but the same dish is similarly v
isible. The RE is also used preferentially in selecting food grains scatter
ed over the floor; RE use in these two contexts is thus associated with vis
ual control which brings the bill in planned contact with a visible target
rather than with approach to a site where it is anticipated that feeding wi
ll occur. Zebrafish also use the RE preferentially when preparing to bite a
target; during purely visual examination of the same target, this preferen
ce disappears. This evidence is used together with evolutionary evidence to
support a new hypothesis for the origin of cerebral lateralization: paired
anterior eyes evolved in filter-feeding ancestors of the vertebrates as pa
rt of the acquisition of prey catching. A key use for early vision was to p
redict likely contact with prey so as to inhibit reflexes of rejection and
avoidance normally elicitated by tactile input to the mouth and so to allow
ingestion. Innervation of mouth structures by the left side of the CNS cau
sed control of mouth reflexes to become predominantly a left CNS affair. As
visual abilities developed this starting condition meant that control of m
anipulation (which is by the mouth for most vertebrates) remained predomina
ntly with the left side of the CNS. (C) 2000 Academic Press.