| Home | [1–10] << 11 12 13 14 15 16 17 18 19 20 >> [21–30] |
|
Cheng, K., & Wignall, A. E. (2006). Honeybees (Apis mellifera) holding on to memories: response competition causes retroactive interference effects. Anim. Cogn., 9(2), 141–150.
Abstract: Five experiments on honeybees examined how the learning of a second task interferes with what was previously learned. Free flying bees were tested for landmark-based memory in variations on a paradigm of retroactive interference. Bees first learned Task 1, were tested on Task 1 (Test 1), then learned Task 2, and were tested again on Task 1 (Test 2). A 60-min delay (waiting in a box) before Test 2 caused no performance decrements. If the two tasks had conflicting response requirements, (e.g., target right of a green landmark in Task 1 and left of a blue landmark in Task 2), then a strong decrement on Test 2 was found (retroactive interference effect). When response competition was minimised during training or testing, however, the decrement on Test 2 was small or nonexistent. The results implicate response competition as a major contributor to the retroactive interference effect. The honeybee seems to hold on to memories; new memories do not wipe out old ones.
|
|
Werner, C., & Rehkämper, G. (2001). Categorization of multidimensional geometrical figures by chickens (Gallus gallus f. domestica): fit of basic assumptions from exemplar, feature and prototype theory. Anim. Cogn., 4(1), 37–48.
Abstract: Five hens, experienced in discrimination of two categories of multidimensional geometrical figures presented in fixed pairs in a simultaneous discrimination, were tested with familiar figures arranged as new pairs to assess the dependence of categorization performance on learned relational or configural cues. Test performance did not differ from training: relational or configural cues still influenced discrimination performance. It was suggested that – in accordance with exemplar theories – this influence depended on differences between pairs of probe exemplars that facilitate retrieval of learned category members. To test whether exemplar, feature or prototype theory was most suitable to explain categorization by chickens, the rates of pecking at exemplars were analysed using principal components analysis (PCA). The distribution of the exemplars' component loads on the single component obtained was examined in the light of the conditions dictated by the three types of theories on how representative category exemplars should be. The least constraining theory, i.e. the exemplar theory, was most suitable. Defining factors of classificatory behaviour are discussed with a special emphasis on the characteristics of category-defining stimulus attributes.
|
|
Vallortigara, G., Regolin, L., Rigoni, M., & Zanforlin, M. (1998). Delayed search for a concealed imprinted object in the domestic chick. Anim. Cogn., 1(1), 17–24.
Abstract: Five-day-old chicks were accustomed to follow an imprinted object (a small red ball with which they had been reared) that was moving slowly in a large arena, until it disappeared behind an opaque screen. In experiments, each chick was initially confined in a transparent cage, from where it could see and track the ball while it moved towards, and then beyond, one of two screens. The screens could be either identical or differ in colour and pattern. Either immediately after the disappearance of the ball, or with a certain delay, the chick was released and allowed to search for its imprinted object behind either screen. The results showed that chicks took into account the directional cue provided by the ball movement and its concealment, up to a delay period of about 180 s, independently of the perceptual characteristics of the two screens. If an opaque partition was positioned in front of the transparent cage immediately after the ball had disappeared, so that, throughout the delay, neither the goal-object nor the two screens were visible, chicks were still capable of remembering and choosing the correct screen, though over a much shorter period of about 60 s. The results suggest that, at least in this precocial bird species, very young chicks can maintain some form of representation of the location where a social partner was last seen, and are also capable of continuously updating this representation so as to take into account successive displacements of the goal-object.
|
|
Lacreuse, A., Martin-Malivel, J., Lange, H. S., & Herndon, J. G. (2007). Effects of the menstrual cycle on looking preferences for faces in female rhesus monkeys. Anim. Cogn., 10(2), 105–115.
Abstract: Fluctuations of ovarian hormones across the menstrual cycle influence a variety of social and cognitive behaviors in primates. For example, female rhesus monkeys exhibit heightened interest for males and increased agonistic interactions with other females during periods of high estrogen levels. In the present study, we hypothesized that females' preference for males during periods of high estrogen levels is also expressed at the level of face perception. We tested four intact females on two face-tasks involving neutral portraits of male and female rhesus monkeys, chimpanzees and humans. In the visual preference task (VP), monkeys had to touch a button to view a face image. The image remained on the screen as long as the button was touched, and the duration of pressing was taken as an index of the monkey's looking time for the face stimulus. In the Face-Delayed Recognition Span Test (Face-DRST), monkeys were rewarded for touching the new face in an increasing number of serially presented faces. Monkeys were tested 5 days a week across one menstrual cycle. Blood was collected every other day for analysis of estradiol and progesterone. Two of the four females were cycling at the time of testing. We did not find an influence of the cycle on Face-DRST, likely due to a floor effect. In the VP however, the two cycling individuals looked longer at conspecific male faces than female faces during the peri-ovulatory period of the cycle. Such effects were absent for human and chimpanzee faces and for the two noncycling subjects. These data suggest that ovarian hormones may influence females' preferences for specific faces, with heightened preference for male faces during the peri-ovulatory period of the cycle. Heightened interest for stimuli of significant reproductive relevance during periods of high conception risk may help guide social and sexual behavior in the rhesus monkey.
|
|
Emery, N. J., Dally, J. M., & Clayton, N. S. (2004). Western scrub-jays ( Aphelocoma californica) use cognitive strategies to protect their caches from thieving conspecifics. Anim. Cogn., 7(1), 37–43.
Abstract: Food caching birds hide food and recover the caches when supplies are less abundant. There is, however, a risk to this strategy because the caches are susceptible to pilfering by others. Corvids use a number of different strategies to reduce possible cache theft. Scrub-jays with previous experience of pilfering other's caches cached worms in two visuospatially distinct caching trays either in private or in the presence of a conspecific. When these storers had cached in private, they subsequently observed both trays out of reach of a conspecific. When these storers had cached in the presence of a conspecific, they subsequently watched the observer pilfering from one of the trays while the other tray was placed in full view, but out of reach. The storers were then allowed to recover the remaining caches 3 h later. Jays cached more worms when they were observed during caching. At the time of recovery, they re-cached more than if they had cached in private, selectively re-caching outside of the trays in sites unbeknown to potential thieves. In addition, after a single pilfering trial, the jays switched their recovery strategy from predominantly checking their caches (i.e. returning to a cache site to see whether the food remained there) to predominantly eating them. Re-caching remained constant across the three trials. These results suggest that scrub-jays use flexible, cognitive caching and recovery strategies to aid in reducing potential future pilfering of caches by conspecifics.
Keywords: Animals; Birds/*physiology; Feeding Behavior/*physiology; Female; *Food; Male; *Memory
|
|
Pepperberg, I. M. (2004). “Insightful” string-pulling in Grey parrots (Psittacus erithacus) is affected by vocal competence. Anim. Cogn., 7(4), 263–266.
Abstract: Four Grey parrots (Psittacus erithacus) were tested on their ability to obtain an item suspended from a string such that mutiple, repeated, coordinated beak-foot actions were required for success (e.g., Heinrich 1995). Those birds with little training in referential English requests (e.g. “I want X”) succeeded, whereas birds who could request the suspended item failed to obtain the object but engaged in repeated requesting.
|
|
Kusayama, T., Bischof, H. - J., & Watanabe, S. (2000). Responses to mirror-image stimulation in jungle crows (Corvus macrorhynchos). Anim. Cogn., 3(1), 61–64.
Abstract: Four jungle crows (Corvus macrorhynchos) were exposed to a mirror placed either vertically or horizontally. The most frequently observed behaviors were pecking at the mirror and wing flapping when looking toward the mirror. These behavior patterns, which were only rarely observed when the mirror was reversed, can be interpreted as aggressive behaviors against a conspecific. The vertical mirror evoked the behaviors more often than the horizontal mirror. The present results suggest that crows perceive their mirror image as an image of a conspecific, not as their own.
|
|
Rasa, O. A. E. (1998). To stay or to leave? Decision rules for partner species relocation in two symbiotic pairs of desert beetles. Anim. Cogn., 1(1), 47–54.
Abstract: Four nocturnal Kalahari desert tenebrionid beetles live in closely associated species pairs. The larger member of each pair, Parastizopus and Gonopus, are the primary burrowers while their smaller associates, Eremostibes and Herpiscius, inhabit the burrows with them and feed on detritus the larger beetles carry in. During summer drought, the two large species have different emergence times, surface activity patterns (vagilities) and different probabilities that burrows will be reoccupied before sunrise or remain empty for longer periods. Because their partners leave the burrows, the smaller species must make a decision either to stay in the expectation of a burrow being reinhabited, or leave and locate a new partner. The vagility and burrow fidelity of the associating species were studied using marked individuals in free-living populations. Field inclusion/exclusion experiments to test what influences the decision process showed that neither continual partner presence nor food induced the smaller beetles to remain. Different percentages, depending on species, left overnight. For both associates, these proportions corresponded exactly to the probability that the burrow would not be inhabited by their partner species the next day. Neither species predicted the probability of burrow reoccupation after a short vacancy and adopted a “waiting” strategy.
|
|
Vonk, J. (2003). Gorilla ( Gorilla gorilla gorilla) and orangutan ( Pongo abelii) understanding of first- and second-order relations. Anim. Cogn., 6(2), 77–86.
Abstract: Four orangutans and one gorilla matched images in a delayed matching-to-sample (DMTS) task based on the relationship between items depicted in those images, thus demonstrating understanding of both first- and second-order relations. Subjects matched items on the basis of identity, color, or shape (first-order relations, experiment 1) or same shape, same color between items (second-order relations, experiment 2). Four of the five subjects performed above chance on the second-order relations DMTS task within the first block of five sessions. High levels of performance on this task did not result from reliance on perceptual feature matching and thus indicate the capability for abstract relational concepts in two species of great ape.
|
|
Potì, P. (2000). Aspects of spatial cognition in capuchins (Cebus apella): frames of reference and scale of space. Anim. Cogn., 3(2), 69–77.
Abstract: Frames of reference (i.e. sets of loci defining spatial locations) determine animals' performances in object search tasks. Reference frames are used at different scales. Although much behavioural research has been conducted on search strategies in many animal species, relatively little has been done on nonhuman primates. The two experiments reported here focused on the relative strength and the level of functioning of different reference frames at the small-scale level in four capuchins (Cebus apella). Two identical boxes and a landmark were placed on a round platform that could be rotated. A reward was hidden in subject's view under one box, and then a sash-screen was lowered to hide the rotation of the platform; the sash-screen was then lifted and the subject allowed to search for the reward. In experiment 1 the rewarded box was always the closer to the landmark, in experiment 2 it could be either the box closer to or the box farther from the landmark. Capuchins were successful after invisible rotations in experiment 1, but they failed after invisible rotations in experiment 2. Two possible explanations are proposed: (1) capuchins relied heavily on the left-right body-axis as a frame, and they could only substitute it with a simple association between the rewarded position and the landmark; or (2) capuchins failed because they chose external cues in the room, therefore on a inappropriate scale. The latter explanation allows two further inferences: (a) the capuchins' choice was indirectly related to their body-axes; and (b) the capuchins revealed a cognitive asymmetry between small-scale and large-scale spaces, thus differing from humans.
|