Visual discrimination of orientation by the goldfish (Carassius auratus).
D000818:Animals; D003216:Conditioning, Operant; D003530:Cyprinidae / Q000502:physiology*; D004056:Differential Threshold; D004192:Discrimination, Psychological; D004777:Environment; D005556:Form Perception; D009949:Orientation; D014785:Vision, Ocular