Abstract: Horses, like other ungulates, are active in the day, at dusk, dawn, and night; and, they have eyes designed to have both high sensitivity for vision in dim light and good visual acuity under higher light levels (Walls, 1942). Typically, daytime activity is associated with the presence of multiple cone classes and color-vision capacity (Jacobs, 1993). Previous studies in other ungulates, such as pigs, goats, cows, sheep and deer, have shown that they have two spectrally different cone types, and hence, at least the photopigment basis for dichromatic color vision (Neitz & Jacobs, 1989; Jacobs, Deegan II, Neitz, Murphy, Miller, & Marchinton, 1994; Jacobs, Deegan II, & Neitz, 1998). Here, electroretinogram flicker photometry was used to measure the spectral sensitivities of the cones in the domestic horse (Equus caballus). Two distinct spectral mechanisms were identified and are consistent with the presence of a short-wavelength-sensitive (S) and a middle-to-long-wavelength-sensitive (M/L) cone. The spectral sensitivity of the S cone was estimated to have a peak of 428 nm, while the M/L cone had a peak of 539 nm. These two cone types would provide the basis for dichromatic color vision consistent with recent results from behavioral testing of horses (Macuda & Timney, 1999; Macuda & Timney, 2000; Timney & Macuda, 2001). The spectral peak of the M/L cone photopigment measured here, in vivo, is similar to that obtained when the gene was sequenced, cloned, and expressed in vitro (Yokoyama & Radlwimmer, 1999). Of the ungulates that have been studied to date, all have the photopigment basis for dichromatic color vision; however, they differ considerably from one another in the spectral tuning of their cone pigments. These differences may represent adaptations to the different visual requirements of different species.

Abstract: Four experiments used a four-choice discrimination learning paradigm to explore the pigeon's recognition of line drawings of four objects (an airplane, a chair, a desk lamp, and a flashlight) that were rotated in depth. The pigeons reliably generalized discriminative responding to pictorial stimuli over all untrained depth rotations, despite the bird's having been trained at only a single depth orientation. These generalization gradients closely resembled those found in prior research that used other stimulus dimensions. Increasing the number of different vantage points in the training set from one to three broadened the range of generalized testing performance, with wider spacing of the training orientations more effectively broadening generalized responding. Template and geon theories of visual recognition are applied to these empirical results.

Abstract: Domestic chicks are capable of perceiving as a whole objects partly concealed by occluders (“amodal completion”). In previous studies chicks were imprinted on a certain configuration and at test they were required to choose between two alternative versions of it. Using the same paradigm we now investigated the presence of hemispheric differences in amodal completion by testing newborn chicks with one eye temporarily patched. Separate groups of newly hatched chicks were imprinted binocularly: (1) on a square partly occluded by a superimposed bar, (2) on a whole or (3) on an amputated version of the square. At test, in monocular conditions, each chick was presented with a free choice between a complete and an amputated square. In the crucial condition 1, chicks tested with only their left eye in use chose the complete square (like binocular chicks would do); right-eyed chicks, in contrast, tended to choose the amputated square. Similar results were obtained in another group of chicks imprinted binocularly onto a cross (either occluded or amputated in its central part) and required to choose between a complete or an amputated cross. Left-eyed and binocular chicks chose the complete cross, whereas right-eyed chicks did not choose the amputated cross significantly more often. These findings suggest that neural structures fed by the left eye (mainly located in the right hemisphere) are, in the chick, more inclined to a “global” analysis of visual scenes, whereas those fed by the right eye seem to be more inclined to a “featural” analysis of visual scenes.

Abstract: Auditory-visual processing of species-specific vocalizations was investigated in a female chimpanzee named Pan. The basic task was auditory-visual matching-to-sample, where Pan was required to choose the vocalizer from two test movies in response to a chimpanzee's vocalization. In experiment 1, movies of vocalizing and silent faces were paired as the test movies. The results revealed that Pan recognized the status of other chimpanzees whether they vocalized or not. In experiment 2, two different types of vocalizing faces of an identical individual were prepared as the test movies. Pan recognized the correspondence between vocalization types and faces. These results suggested that chimpanzees possess crossmodal representations of their vocalizations, as do humans. Together with the ability of vocal individual recognition, this ability might reflect chimpanzees' profound understanding of the status of other individuals.

Abstract: Because most learning studies in cephalopods have been performed on octopods, it remains unclear whether such abilities are specific to octopus, or whether they correlate with having a larger and more centrally organized brain. To investigate associative learning in a different cephalopod, six sexually mature cuttlefish (Sepia officinalis) participated in a counterbalanced, within-subjects, appetitive, classical conditioning procedure. Two plastic spheres (conditioned stimuli, CSs), differing in brightness, were presented sequentially. Presentation of the CS+ was followed 5 s later by a live feeder fish (unconditioned stimulus, US). Cuttlefish began to attack the CS+ with the same type of food-acquisition seizures used to capture the feeder fish. After seven blocks of training (42 presentations of each CS) the difference in seizure probability between CS+ and CS- trials more than doubled; and was found to be significantly higher in late versus early blocks. These results indicate that cuttlefish exhibit autoshaping under some conditions. The possible ecological significance of this type of learning is briefly discussed.