Abstract: Eight mares were tested to determine if they remained near one of two stallions longer than would be expected if association was random. Six stallions were paired in 30 combinations and each mare was tested 30 times. The mares (Equus caballus) demonstrated a definite preference for individual stallions throughout the breeding season. This preference was influenced by the estrous state of the mare. During estrus, mares' preferences for stallions were positively correlated with the rate at which a given stallion vocalized. During diestrus, mares spent significantly less time in the proximity of stallions and did not exhibit any preference for individual stallions.

Abstract: We examined the ability of domestic dogs to choose the larger versus smaller quantity of food in two experiments. In experiment 1, we investigated the ability of 29 dogs (results from 18 dogs were used in the data analysis) to discriminate between two quantities of food presented in eight different combinations. Choices were simultaneously presented and visually available at the time of choice. Overall, subjects chose the larger quantity more often than the smaller quantity, but they found numerically close comparisons more difficult. In experiment 2, we tested two dogs from experiment 1 under three conditions. In condition 1, we used similar methods from experiment 1 and tested the dogs multiple times on the eight combinations from experiment 1 plus one additional combination. In conditions 2 and 3, the food was visually unavailable to the subjects at the time of choice, but in condition 2, food choices were viewed simultaneously before being made visually unavailable, and in condition 3, they were viewed successively. In these last two conditions, and especially in condition 3, the dogs had to keep track of quantities mentally in order to choose optimally. Subjects still chose the larger quantity more often than the smaller quantity when the food was not simultaneously visible at the time of choice. Olfactory cues and inadvertent cuing by the experimenter were excluded as mechanisms for choosing larger quantities. The results suggest that, like apes tested on similar tasks, some dogs can form internal representations and make mental comparisons of quantity.

Abstract: Several studies have demonstrated that mammals, birds and fish use comparable spatial learning strategies. Unfortunately, except in insects, few studies have investigated spatial learning mechanisms in invertebrates. Our study aimed to identify the strategies used by cuttlefish (Sepia officinalis) to solve a spatial task commonly used with vertebrates. A new spatial learning procedure using a T-maze was designed. In this maze, the cuttlefish learned how to enter a dark and sandy compartment. A preliminary test confirmed that individual cuttlefish showed an untrained side-turning preference (preference for turning right or left) in the T-maze. This preference could be reliably detected in a single probe trial. In the following two experiments, each individual was trained to enter the compartment opposite to its side-turning preference. In Experiment 1, distal visual cues were provided around the maze. In Experiment 2, the T-maze was surrounded by curtains and two proximal visual cues were provided above the apparatus. In both experiments, after acquisition, strategies used by cuttlefish to orient in the T-maze were tested by creating a conflict between the formerly rewarded algorithmic behaviour (turn, response learning) and the visual cues identifying the goal (place learning). Most cuttlefish relied on response learning in Experiment 1; the two strategies were used equally often in Experiment 2. In these experiments, the salience of cues provided during the experiment determined whether cuttlefish used response or place learning to solve this spatial task. Our study demonstrates for the first time the presence of multiple spatial strategies in cuttlefish that appear to closely parallel those described in vertebrates.

Abstract: Previous research suggests that chimpanzees understand single invisible displacement. However, this Piagetian task may be solvable through the use of simple search strategies rather than through mentally representing the past trajectory of an object. Four control conditions were thus administered to two chimpanzees in order to separate associative search strategies from performance based on mental representation. Strategies involving experimenter cue-use, search at the last or first box visited by the displacement device, and search at boxes adjacent to the displacement device were systematically controlled for. Chimpanzees showed no indications of utilizing these simple strategies, suggesting that their capacity to mentally represent single invisible displacements is comparable to that of 18-24-month-old children.

Abstract: Most birds rely on imprinting and experience with conspecifics to learn species-specific recognition cues. Australian brush-turkeys (Alectura lathami) do not imprint and form no bonds with parents. They hatch asynchronously, disperse widely and meet juvenile conspecifics at an unpredictable age. Nevertheless, in captivity, hatchlings respond to other chicks. A recent study, which involved the use of robotic models, found that chicks prefer to approach robots that emit specific visual cues. Here, we evaluated their response to acoustic cues, which usually play an important role in avian social cognition. However, in simultaneous choice tests, neither 2-day-old nor 9-day-old chicks preferred the choice arm with playback of either chick or adult conspecific calls over the arm containing a silent loudspeaker. Chicks of both age classes, however, scanned their surroundings more during chick playback, and the response was thus consistent in younger and older chicks. We also presented the chicks with robotic models, either with or without playback of chick calls. They did not approach the calling robot more than they did the silent robot, indicating that the combination of visual and acoustic cues does not evoke a stronger response. These results will allow further comparison with species that face similar cognitive demands in the wild, such as brood parasites. Such a comparative approach, which is the focus of cognitive ecology, will enable us to further analyse the evolution and adaptive value of species recognition abilities.