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Acuna, B. D., Sanes, J. N., & Donoghue, J. P. (2002). Cognitive mechanisms of transitive inference. Exp Brain Res, 146(1), 1–10.
Abstract: We examined how the brain organizes interrelated facts during learning and how the facts are subsequently manipulated in a transitive inference (TI) paradigm (e.g., if A<B and B<C, then A<C). This task determined features such as learned facts and behavioral goals, but the learned facts could be organized in any of several ways. For example, if one learns a list by operating on paired items, the pairs may be stored individually as separate facts and reaction time (RT) should decrease with learning. Alternatively, the pairs may be stored as a single, unified list, which may yield a different RT pattern. We characterized RT patterns that occurred as participants learned, by trial and error, the predetermined order of 11 shapes. The task goal was to choose the shape occurring closer to the end of the list, and feedback about correctness was provided during this phase. RT increased even as its variance decreased during learning, suggesting that the learnt knowledge became progressively unified into a single representation, requiring more time to manipulate as participants acquired relational knowledge. After learning, non-adjacent (NA) list items were presented to examine how participants reasoned in a TI task. The task goal also required choosing from each presented pair the item occurring closer to the list end, but without feedback. Participants could solve the TI problems by applying formal logic to the previously learnt pairs of adjacent items; alternatively, they could manipulate a single, unified representation of the list. Shorter RT occurred for NA pairs having more intervening items, supporting the hypothesis that humans employ unified mental representations during TI. The response pattern does not support mental logic solutions of applying inference rules sequentially, which would predict longer RT with more intervening items. We conclude that the brain organizes information in such a way that reflects the relations among the items, even if the facts were learned in an arbitrary order, and that this representation is subsequently used to make inferences.
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Carroll, J., Murphy, C. J., Neitz, M., Hoeve, J. N., & Neitz, J. (2001). Photopigment basis for dichromatic color vision in the horse. J Vis, 1(2), 80–87.
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.
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Hall, C. A., Cassaday, H. J., & Derrington, A. M. (2003). The effect of stimulus height on visual discrimination in horses. J. Anim Sci., 81(7), 1715–1720.
Abstract: This study investigated the effect of stimulus height on the ability of horses to learn a simple visual discrimination task. Eight horses were trained to perform a two-choice, black/white discrimination with stimuli presented at one of two heights: ground level or at a height of 70 cm from the ground. The height at which the stimuli were presented was alternated from one session to the next. All trials within a single session were presented at the same height. The criterion for learning was four consecutive sessions of 70% correct responses. Performance was found to be better when stimuli were presented at ground level with respect to the number of trials taken to reach the criterion (P < 0.05), percentage of correct first choices (P < 0.01), and repeated errors made (P < 0.01). Thus, training horses to carry out tasks of visual discrimination could be enhanced by placing the stimuli on the ground. In addition, the results of the present study suggest that the visual appearance of ground surfaces is an important factor in both horse management and training.
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Parr, L. A. (2004). Perceptual biases for multimodal cues in chimpanzee (Pan troglodytes) affect recognition. Anim. Cogn., 7(3), 171–178.
Abstract: The ability of organisms to discriminate social signals, such as affective displays, using different sensory modalities is important for social communication. However, a major problem for understanding the evolution and integration of multimodal signals is determining how humans and animals attend to different sensory modalities, and these different modalities contribute to the perception and categorization of social signals. Using a matching-to-sample procedure, chimpanzees discriminated videos of conspecifics' facial expressions that contained only auditory or only visual cues by selecting one of two facial expression photographs that matched the expression category represented by the sample. Other videos were edited to contain incongruent sensory cues, i.e., visual features of one expression but auditory features of another. In these cases, subjects were free to select the expression that matched either the auditory or visual modality, whichever was more salient for that expression type. Results showed that chimpanzees were able to discriminate facial expressions using only auditory or visual cues, and when these modalities were mixed. However, in these latter trials, depending on the expression category, clear preferences for either the visual or auditory modality emerged. Pant-hoots and play faces were discriminated preferentially using the auditory modality, while screams were discriminated preferentially using the visual modality. Therefore, depending on the type of expressive display, the auditory and visual modalities were differentially salient in ways that appear consistent with the ethological importance of that display's social function.
Keywords: Acoustic Stimulation; *Animal Communication; Animals; Auditory Perception/physiology; Cues; Discrimination Learning/*physiology; Facial Expression; Female; Male; Pan troglodytes/*psychology; Perceptual Masking/*physiology; Photic Stimulation; Recognition (Psychology)/*physiology; Visual Perception/physiology; *Vocalization, Animal
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Izumi, A., & Kojima, S. (2004). Matching vocalizations to vocalizing faces in a chimpanzee (Pan troglodytes). Anim. Cogn., 7(3), 179–184.
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.
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Regolin, L., Marconato, F., & Vallortigara, G. (2004). Hemispheric differences in the recognition of partly occluded objects by newly hatched domestic chicks (Gallus gallus). Anim. Cogn., 7(3), 162–170.
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.
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Zentall, T. R. (2005). Configural/holistic processing or differential element versus compound similarity. Anim. Cogn., 8(2), 141–142.
Abstract: Before accepting a configural or holistic account of visual perception, one should be sure that an analytic (elemental) account does not provide an equal or better explanation of the results. I suggest that when one forms a compound of a color and a line orientation with one element previously trained as an S+ and the other as an S-, the resulting transfer found will depend on the relative salience of the two elements, and most important, the similarity of the compound to each of the training stimuli. Thus, if a line orientation is placed on a colored background (a separable compound), it will appear more like the colored field used in training, and color will control responding. However, if the line itself is colored (an integral compound), the compound will appear more like the line used in training, and line orientation will control responding. Not only does this account do a better job of explaining the data but it is simpler and it is testable.
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Werner, C. W., Tiemann, I., Cnotka, J., & Rehkamper, G. (2005). Do chickens (Gallus gallus f. domestica) decompose visual figures? Anim. Cogn., 8(2), 129–140.
Abstract: To investigate whether learning to discriminate between visual compound stimuli depends on decomposing them into constituting features, hens were first trained to discriminate four features (red, green, horizontal, vertical) from two dimensions (colour, line orientation). After acquisition, hens were trained with compound stimuli made up from these dimensions in two ways: a separable (line on a coloured background) stimulus and an integral one (coloured line). This compound training included a reversal of reinforcement of only one of the two dimensions (half-reversal). After having achieved the compound stimulus discrimination, a second dimensional training identical to the first was performed. Finally, in the second compound training the other dimension was reversed. Two major results were found: (1) an interaction between the dimension reversed and the type of compound stimulus: in compound training with colour reversal, separable compound stimuli were discriminated worse than integral compounds and vice versa in compound training with line orientation reversed. (2) Performance in the second compound training was worse than in the first one. The first result points to a similar mode of processing for separable and integral compounds, whereas the second result shows that the whole stimulus is psychologically superior to its constituting features. Experiment 2 repeated experiment 1 using line orientation stimuli of reversed line and background brightness. Nevertheless, the results were similar to experiment 1. Results are discussed in the framework of a configural exemplar theory of discrimination that assumes the representation of the whole stimulus situation combined with transfer based on a measure of overall similarity.
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Cole, P. D., & Adamo, S. A. (2005). Cuttlefish (Sepia officinalis: Cephalopoda) hunting behavior and associative learning. Anim. Cogn., 8(1), 27–30.
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.
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Heschl, A., & Burkart, J. (2006). A new mark test for mirror self-recognition in non-human primates. Primates, 47(3), 187–198.
Abstract: For 30 years Gallup's (Science 167:86-87, 1970) mark test, which consists of confronting a mirror-experienced test animal with its own previously altered mirror image, usually a color mark on forehead, eyebrow or ear, has delivered valuable results about the distribution of visual self-recognition in non-human primates. Chimpanzees, bonobos, orangutans and, less frequently, gorillas can learn to correctly understand the reflection of their body in a mirror. However, the standard version of the mark test is good only for positively proving the existence of self-recognition. Conclusive statements about the lack of self-recognition are more difficult because of the methodological constraints of the test. This situation has led to a persistent controversy about the power of Gallup's original technique. We devised a new variant of the test which permits more unequivocal decisions about both the presence and absence of self-recognition. This new procedure was tested with marmoset monkeys (Callithrix jacchus), following extensive training with mirror-related tasks to facilitate performance in the standard mark test. The results show that a slightly altered mark test with a new marking substance (chocolate cream) can help to reliably discriminate between true negative results, indicating a real lack of ability to recognize oneself in a mirror, from false negative results that are due to methodological particularities of the standard test. Finally, an evolutionary hypothesis is put forward as to why many primates can use a mirror instrumentally – i.e. know how to use it for grasping at hidden objects – while failing in the decisive mark test.
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