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Pepperberg, I. M., & Brezinsky, M. V. (1991). Acquisition of a relative class concept by an African gray parrot (Psittacus erithacus): discriminations based on relative size. J Comp Psychol, 105(3), 286–294.
Abstract: We report that an African gray parrot (Psittacus erithacus), Alex, responds to stimuli on a relative basis. Previous laboratory studies with artificial stimuli (such as pure tones) suggest that birds make relational responses as a secondary strategy, only after they have acquired information about the absolute values of the stimuli. Alex, however, after learning to respond to a small set of exemplars on the basis of relative size, transferred this behavior to novel situations that did not provide specific information about the absolute values of the stimuli. He responded to vocal questions about which was the larger or smaller exemplar by vocally labeling its color or material, and he responded “none” if the exemplars did not differ in size. His overall accuracy was 78.7%.
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Reid, P. J., & Shettleworth, S. J. (1992). Detection of cryptic prey: search image or search rate? J Exp Psychol Anim Behav Process, 18(3), 273–286.
Abstract: Animals' improvement in capturing cryptic prey with experience has long been attributed to a perceptual mechanism, the specific search image. Detection could also be improved by adjusting rate of search. In a series of studies using both naturalistic and operant search tasks, pigeons searched for wheat, dyed to produce 1 conspicuous and 2 equally cryptic prey types. Contrary to the predictions of the search-rate hypothesis, pigeons given a choice between the 2 cryptic types took the type experienced most recently. However, experience with 1 cryptic type improved accuracy on the other cryptic type, a result inconsistent with a search image specific to 1 prey type. Search image may better be thought of as priming of attention to those features of the prey type that best distinguish the prey from the background.
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Fiset, S., Landry, F., & Ouellette, M. (2006). Egocentric search for disappearing objects in domestic dogs: evidence for a geometric hypothesis of direction. Anim. Cogn., 9(1), 1–12.
Abstract: In several species, the ability to locate a disappearing object is an adaptive component of predatory and social behaviour. In domestic dogs, spatial memory for hidden objects is primarily based on an egocentric frame of reference. We investigated the geometric components of egocentric spatial information used by domestic dogs to locate an object they saw move and disappear. In experiment 1, the distance and the direction between the position of the animal and the hiding location were put in conflict. Results showed that the dogs primarily used the directional information between their own spatial coordinates and the target position. In experiment 2, the accuracy of the dogs in finding a hidden object by using directional information was estimated by manipulating the angular deviation between adjacent hiding locations and the position of the animal. Four angular deviations were tested: 5, 7.5, 10 and 15 degrees . Results showed that the performance of the dogs decreased as a function of the angular deviations but it clearly remained well above chance, revealing that the representation of the dogs for direction is precise. In the discussion, we examine how and why domestic dogs determine the direction in which they saw an object disappear.
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Shettleworth, S. J. (1985). Foraging, memory, and constraints on learning. Ann N Y Acad Sci, 443, 216–226.
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Vlasak, A. N. (2006). Global and local spatial landmarks: their role during foraging by Columbian ground squirrels (Spermophilus columbianus). Anim. Cogn., 9(1), 71–80.
Abstract: Locating food and refuge is essential for an animal's survival. However, little is known how mammals navigate under natural conditions and cope with given environmental constraints. In a series of six experiments, I investigated landmark-based navigation in free-ranging Columbian ground squirrels (Spermophilus columbianus). Squirrels were trained individually to find a baited platform within an array of nine identical platforms and artificial landmarks set up on their territories. After animals learned the location of the food platform in the array, the position of the latter with respect to local artificial, local natural, and global landmarks was manipulated, and the animal's ability to find the food platform was tested. When only positions of local artificial landmarks were changed, squirrels located food with high accuracy. When the location of the array relative to global landmarks was altered, food-finding accuracy decreased but remained significant. In the absence of known global landmarks, the presence of a familiar route and natural local landmarks resulted in significant but not highly accurate performance. Squirrels likely relied on multiple types of cues when orienting towards a food platform. Local landmarks were used only as a secondary mechanism of navigation, and were not attended to when a familiar route and known global landmarks were present. This study provided insights into landmark use by a wild mammal in a natural situation, and it demonstrated that an array of platforms can be employed to investigate landmark-based navigation under such conditions.
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Hampton, R. R., & Shettleworth, S. J. (1996). Hippocampal lesions impair memory for location but not color in passerine birds. Behav Neurosci, 110(4), 831–835.
Abstract: The effects of hippocampal complex lesions on memory for location and color were assessed in black-capped chickadees (Parus atricapillus) and dark-eyed juncos (Junco hyemalis) in operant tests of matching to sample. Before surgery, most birds were more accurate on tests of memory for location than on tests of memory for color. Damage to the hippocampal complex caused a decline in memory for location, whereas memory for color was not affected in the same birds. This dissociation indicates that the avian hippocampus plays an important role in spatial cognition and suggests that this brain structure may play no role in working memory generally.
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Hampton, R. R., Sherry, D. F., Shettleworth, S. J., Khurgel, M., & Ivy, G. (1995). Hippocampal volume and food-storing behavior are related in parids. Brain Behav Evol, 45(1), 54–61.
Abstract: The size of the hippocampus has been previously shown to reflect species differences and sex differences in reliance on spatial memory to locate ecologically important resources, such as food and mates. Black-capped chickadees (Parus atricapillus) cached more food than did either Mexican chickadees (P. sclateri) or bridled titmice (P. wollweberi) in two tests of food storing, one conducted in an aviary and another in smaller home cages. Black-capped chickadees were also found to have a larger hippocampus, relative to the size of the telencephalon, than the other two species. Differences in the frequency of food storing behavior among the three species have probably produced differences in the use of hippocampus-dependent memory and spatial information processing to recover stored food, resulting in graded selection for size of the hippocampus.
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Hampton, R. R., & Shettleworth, S. J. (1996). Hippocampus and memory in a food-storing and in a nonstoring bird species. Behav Neurosci, 110(5), 946–964.
Abstract: Food-storing birds maintain in memory a large and constantly changing catalog of the locations of stored food. The hippocampus of food-storing black-capped chickadees (Parus atricapillus) is proportionally larger than that of nonstoring dark-eyed juncos (Junco hyemalis). Chickadees perform better than do juncos in an operant test of spatial non-matching-to-sample (SNMTS), and chickadees are more resistant to interference in this paradigm. Hippocampal lesions attenuate performance in SNMTS and increase interference. In tests of continuous spatial alternation (CSA), juncos perform better than chickadees. CSA performance also declines following hippocampal lesions. By itself, sensitivity of a given task to hippocampal damage does not predict the direction of memory differences between storing and nonstoring species.
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Rilling, M. E., & Neiworth, J. J. (1991). How animals use images. Sci Prog, 75(298 Pt 3-4), 439–452.
Abstract: Animal cognition is a field within experimental psychology in which cognitive processes formerly studied exclusively with people have been demonstrated in animals. Evidence for imagery in the pigeon emerges from the experiments described here. The pigeon's task was to discriminate, by pecking the appropriate choice key, between a clock hand presented on a video screen that rotated clockwise with constant velocity from a clock hand that violated constant velocity. Imagery was defined by trials on which the line rotated from 12.00 o'clock to 3.00 o'clock, then disappeared during a delay, and reappeared at a final stop location beyond 3.00 o'clock. After acquisition of a discrimination with final stop locations at 3.00 o'clock and 6.00 o'clock, the evidence for imagery was the accurate responding of the pigeons to novel locations at 4.00 o'clock and 7.00 o'clock. Pigeons display evidence of imagery by transforming a representation of movement that includes a series of intermediate steps which accurately represent the location of a moving stimulus after it disappears.
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Shettleworth, S. J., & Krebs, J. R. (1982). How marsh tits find their hoards: the roles of site preference and spatial memory. J Exp Psychol Anim Behav Process, 8(4), 354–375.
Abstract: Marsh tits (Parus palustris) store single food items in scattered locations and recover them hours or days later. Some properties of the spatial memory involved were analyzed in two laboratory experiments. In the first, marsh tits were offered 97 sites for storing 12 seeds. They recovered a median of 65% of them 2-3 hr later, making only two errors per seed while doing so. Over trials, they used some sites more often than others, but during recovery they were more likely to visit a site of any preference value if they had stored a seed there that day than if they had not. Recovery performance was much worse if the experimenters moved the seeds between storage and recovery. A fixed search strategy that had some of the same average properties as the tits' search behavior also did worse than the real birds. In Experiment 2, any tendency to visit the same sites on successive daily tests in the aviary was placed in opposition to memory for storage sites by allowing the tits to store more seeds 2 hr after storing a first batch. They tended to avoid individual storage sites holding seeds from the first batch. When the tits searched for all the seeds 2 hr later, they tended to recover more seeds from the second batch than from the first, i.e., there was a recency effect.
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