pubmed-article:6539458 | pubmed:abstractText | Pigeons' head-in-space and eye-in-head positions were simultaneously recorded (EOG) in video during feeding. A linear correlation was found between the experimentally measured eye convergence (sum of both EOGs ) and grain parallax (calculated from interocular and eye-to-grain distances). This graded convergence of the eyes on approaching a target is considered evidence of frontal binocular fixation. Since such convergence prevails when the animal is forced to rely on frontal monocular or on lateral vision, a central mechanism controlling frontal fixation in the pigeon must be presupposed . | lld:pubmed |