Abstract: Two series of experiments investigated factors affecting utterance of food calls in the domestic hen, Gallus domesticus. The first series of experiments tested the effect of food preference and the hen’s internal state on the utterance of food calls. Different food types were presented first singly and then in a choice test to 20 hens, first when hens were laying, and then when they were maternal. The second series of experiments tested the effect of hunger level on the utterance of food calls in laying hens, and maternal hens with or without chicks. These two series of experiments showed that laying hens and maternal hens showed a similar marked preference for certain types of food, but laying hens very rarely emitted food calls, in contrast to maternal hens. This shows the effect of the bird’s psychophysiological state on her tendency to emit food calls. The more a maternal hen preferred a food type, the more food calls she emitted. This was observed from the beginning of a test in single-food tests as well as in choice tests. Hunger level positively affected food-call production under certain feeding conditions in maternal hens, but not in laying hens. When maternal hens were tested in the absence of their chicks, utterance of food calls was more sustained than in the presence of chicks.

Abstract: One adult female chimpanzee (Pan troglodytes) was trained to respond serially to three arabic numerals between 1 and 9, presented on a cathode-ray-tube (CRT) screen. To examine the factors affecting her sequential responding behavior, wild-card items were added to the three-item sequences. When this wild-card item remained until the subject responded to the last numeral (i.e., the terminator condition), her response to the terminator at each point of the sequence was controlled by the ordinal distance between numerals. Thus, the number of responses to the terminator increased as the ordinal distance between numerals increased. When the wild-card item was eliminated by the subject's response (wild-card conditions), the probability of responses to the wild card before the first numeral increased as a function of the serial position of the first numeral. These results were consistent with previous studies of response time and suggest both serial position and symbolic distance effects. It is suggested that the subject might form the integrated 9-item linear representations by training of possible subsets of three-item sequences. Knowledge concerning the ordinal position of each numeral was established through this training.

Abstract: Abstract  Transitive performance (TP) is a learning-based behaviour exhibited by a wide range of species, where if a subject has been taught to prefer A when presented with the pair AB but to prefer B when presented with the pair BC, then the subject will also prefer A when presented with the novel pair AC. Most explanations of TP assume that subjects recognize and learn an underlying sequence from observing the training pairs. However, data from squirrel monkeys (Saimiri sciureus) and young children contradict this, showing that when three different items (a triad) are drawn from the sequence, subjects`` performance degrades systematically (McGonigle and Chalmers, Nature 267:694-696, 1977; Chalmers and McGonigle, Journal of Experimental Child Psychology 37:355-377, 1984; Harris and McGonigle, The Quarterly Journal of Experimental Psychology 47B:319-348, 1994). We present here the two-tier model, the first learning model of TP which accounts for this systematic performance degradation. Our model assumes primate TP is based on a general-purpose task learning system rather than a special-purpose sequence-learning system. It supports the hypothesis of Heckers et al. (Hippocampus 14:153-162, 2004) that TP is an expression of two separate general learning elements: one for associating actions and contexts, another for prioritising associations when more than one context is present. The two-tier model also provides explanations for why phased training is important for helping subjects learn the initial training pairs and why some subjects fail to do so. It also supports the Harris and McGonigle (The Quarterly Journal of Experimental Psychology 47B:319-348, 1994) explanation of why, once the training pairs have been acquired, subjects perform transitive choice automatically on two-item diads, but not when exposed to triads from the same sequence.

Abstract: Abstract: One advantage of living in a social group is the opportunity to use information provided by other individuals. Social information can be based on cues provided by a conspecific or even by a heterospecific individual (e.g., gaze direction, vocalizations, pointing gestures). Although the use of human gaze and gestures has been extensively studied in primates, and is increasingly studied in other mammals, there is no documentation of birds using these cues in a cooperative context. In this study, we tested the ability of three African gray parrots to use different human cues (pointing and/or gazing) in an object-choice task. We found that one subject spontaneously used the most salient pointing gesture (looking and steady pointing with hand at about 20 cm from the baited box). The two others were also able to use this cue after 15 trials. None of the parrots spontaneously used the steady gaze cues (combined head and eye orientation), but one learned to do so effectively after only 15 trials when the distance between the head and the baited box was about 1 m. However, none of the parrots were able to use the momentary pointing nor the distal pointing and gazing cues. These results are discussed in terms of sensitivity to joint attention as a prerequisite to understand pointing gestures as it is to the referential use of labels.

Abstract: Being able to recognize the faces of our friends and family members no matter where we see them represents a substantial challenge for the visual system because the retinal image of a face can be degraded by both changes in the person (age, expression, pose, hairstyle, etc.) and changes in the viewing conditions (direction and degree of illumination). Yet most of us are able to recognize familiar people effortlessly. A popular theory for how face recognition is achieved has argued that the brain stabilizes facial appearance by building average representations that enhance diagnostic features that reliably vary between people while diluting features that vary between instances of the same person. This explains why people find it easier to recognize average images of people, created by averaging multiple images of the same person together, than single instances (i.e. photographs). Although this theory is gathering momentum in the psychological and computer sciences, there is no evidence of whether this mechanism represents a unique specialization for individual recognition in humans. Here we tested two species, chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta), to determine whether average images of different familiar individuals were easier to discriminate than photographs of familiar individuals. Using a two-alternative forced-choice, match-to-sample procedure, we report a behaviour response profile that suggests chimpanzees encode the faces of conspecifics differently than rhesus monkeys and in a manner similar to humans.