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| Author |
Todd, I.A.; Kacelnik, A. |
| Title |
Psychological mechanisms and the Marginal Value Theorem: dynamics of scalar memory for travel time |
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Journal Article |
| Year |
1993 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
46 |
Issue |
4 |
Pages  |
765-775 |
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Abstract. The relation between memory for travel time and foraging decisions was studied experimentally. The temporal properties of two environments with patchily distributed food were simulated in the laboratory using pigeons, Columba livia, as subjects. The two environments differed in mean travel time, while the coefficient of variation of travel time and the decelerated function relating cumulative food gain to time in the patch were held constant within and between environments. Each environment contained a uniform mixture of five travel times experienced in a random order. Two of the five travel times were common in both environments. Effects of travel time were studied by comparing prey collected per patch visit (PPV) after various travel times within each environment, and by comparing patch exploitation after equal travel times between environments. Within the environment with long mean travel time (LMT) PPV was positively correlated with the last and the penultimate travel times but not with travel times before that. The increase in PPV per second of last travel time was six times greater than the increase per second of penultimate travel time, implying very steep memory discounting. In the environment with short mean travel time (SMT), there was no correlation between PPV and previous travel times. However, comparisons between environments of visits following travel times common to both environments (thus removing the effect of the last travel time) showed that substantially more prey were taken after equal travel times in the LMT than in the SMT environment. This difference cannot be accounted for by the within-environment effect of penultimate travel time, implying that there is a different, less steeply devalued, effect of the mixture of travel times. A model of information processing based on combining Scalar Expectancy Theory with the predictions of rate maximization under the Marginal Value Theorem is presented. The model can approximate the results obtained in this and previous experiments and provides a framework for further analysis of memory mechanisms of foraging behaviour. |
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2111 |
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Roberts, J.; Hunter, M.L.; Kacelnik, A. |
| Title |
The ground effect and acoustic communication |
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Journal Article |
| Year |
1981 |
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Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
29 |
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2 |
Pages |
633-634 |
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2123 |
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Cuthill, I.C.; Kacelnik, A.; Krebs, J.R.; Haccou, P.; Iwasa, Y. |
| Title |
Starlings exploiting patches: the effect of recent experience on foraging decisions |
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Journal Article |
| Year |
1990 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
40 |
Issue |
4 |
Pages |
625-640 |
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Laboratory and field experiments have shown that, as predicted by the marginal value model, starlings, Sturnus vulgaris, stay longer in a food patch when the average travel time between patches is long. A laboratory analogue of a patchy environment was used to investigate how starlings respond to rapidly fluctuating changes in travel time in order to find out the length of experience over which information is integrated. When there was a progressive increase in the amount of work required to obtain successive food items in a patch (experiment 1), birds consistently took more prey after long than after short travel times; travel experience before the most recent had no effect on the number of prey taken. Such behaviour does not maximize the rate of energy intake in this environment. The possibility that this is the result of a simple constraint on crop capacity is rejected as, when successive prey were equally easy to obtain up until a stepwise depletion of the patch (experiment 2), birds took equal numbers of prey per visit after long and short travel times: the rate-maximizing behaviour. A series of models are developed to suggest the possible constraints on optimal behaviour that affect starlings in the type of environment mimicked by experiment 1. |
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2118 |
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Kacelnik, A.; Houston, A.I. |
| Title |
Some effects of energy costs on foraging strategies |
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Journal Article |
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1984 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
32 |
Issue |
2 |
Pages |
609-614 |
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We consider the effect of including energy costs on the optimal strategy for animals exploiting a depleting food resource. In the context of central place foraging this leads to the problem of what load size should be brought back to the central place. Two strategies are discussed: (i) maximize gross rate of energy delivery and (ii) maximize net rate of energy delivery. The optimal load size (or optimal patch time) for net maximizers is not always larger than for gross maximizers, as has been claimed. Instead, the difference in optimal load size has the same sign as the difference between metabolic rates of travelling and foraging. We point out that the influence of costs has not always been correctly incorporated in experimental tests of the theory. |
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2122 |
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Kacelnik, A. |
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R.C. Bolies and M.D. Beecher, Editors, Evolution and Learning, Lawrence Erlbaum, Hillsdale, New Jersey (1988), p. x |
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Journal Article |
| Year |
1990 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
40 |
Issue |
3 |
Pages |
602-603 |
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no |
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2119 |
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Brunner, D.; Kacelnik, A.; Gibbon, J. |
| Title |
Optimal foraging and timing processes in the starling, Sturnus vulgaris: effect of inter-capture interval |
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Journal Article |
| Year |
1992 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
44 |
Issue |
4 |
Pages |
597-613 |
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Laboratory experiments with starlings, Sturnus vulgaris, were conducted to investigate the interaction between timing and cost-benefit considerations. The design simulated an environment in which food was distributed in patches. Patches contained a random number of food items (N=0-4) separated by a fixed inter-capture interval or fixed interval. All patches ended with sudden depletion. The time elapsed since the last prey capture was the only way to detect the depletion of the patch. Once the patch was depleted a new patch could be reached by travelling between two perches. Three measures of timing were taken: (1) rate of working for food as function of `waiting' time in a patch, (2) the time of the last response in a patch or `giving-in' time, and (3) the time at which travel was initiated or `moving-on' time. The fixed interval that characterized patches was varied between conditions. The mean time of the peak in working rate was consistently centred around the fixed interval, while the other two measures of timing kept a roughly linear relation to the fixed interval, with slope greater than one. In accordance with Scalar Expectancy Theory, variability in the three forms of timing was proportional to the magnitude of the fixed interval. The birds seemed to take account of this increase in variability as shown by the mean value of their giving-up criterion. These results imply that information-processing constraints are important for modelling behavioural optimality. |
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no |
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2112 |
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Pompilio, L.; Kacelnik, A. |
| Title |
State-dependent learning and suboptimal choice: when starlings prefer long over short delays to food |
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Journal Article |
| Year |
2005 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
70 |
Issue |
3 |
Pages |
571-578 |
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Recent studies have used labels such as `work ethics', `sunk costs' and `state-dependent preferences' for apparent anomalies in animals' choices. They suggest that preference between options relates to the options' history, rather than depending exclusively on the expected payoffs. For instance, European starlings, Sturnus vulgaris, trained to obtain identical food rewards from two sources while in two levels of hunger preferred the food source previously associated with higher hunger, regardless of the birds' state at the time of testing. We extended this experimentally and theoretically by studying starlings choosing between sources that differed not only in history but also in the objective properties (delay until reward) of the payoffs they delivered. Two options (PF and H) were initially presented in single-option sessions when subjects were, respectively, prefed or hungry. While option PF offered a delay until reward of 10 s in all treatments, option H delivered delays of 10, 12.5, 15 and 17.5 s in four treatments. When training was completed, we tested preference between the options. When delays in both options were equal (10 s), the birds strongly preferred H. When delay in H was 17.5 s, the birds were indifferent, with intermediate results for intermediate treatments. Preference was not mediated by disrupted knowledge of the delays. Thus, preferences were driven by past state-dependent gains, rather than by the joint effect of the birds' state at the time of choice and knowledge of the absolute properties of each alternative, as assumed in state-dependent, path-independent models of optimal choice. |
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2104 |
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Reboreda, J.C.; Clayton, N.S.; Kacelnik, A. |
| Title |
Species and sex differences in hippocampus size in parasitic and non-parasitic cowbirds |
Type |
Journal Article |
| Year |
1996 |
Publication |
Neuroreport |
Abbreviated Journal |
Neuroreport |
| Volume |
7 |
Issue |
2 |
Pages |
505-508 |
| Keywords |
Animals; Birds/*physiology; Female; Hippocampus/*anatomy & histology; Male; Nesting Behavior/*physiology; Sex Characteristics; Species Specificity; Telencephalon/anatomy & histology |
| Abstract |
To test the hypothesis that selection for spatial abilities which require birds to locate and to return accurately to host nests has produced an enlarged hippocampus in brood parasites, three species of cowbird were compared. In shiny cowbirds, females search for host nests without the assistance of the male; in screaming cowbirds, males and females inspect hosts' nests together; in bay-winged cowbirds, neither sex searches because this species is not a brood parasite. As predicted, the two parasitic species had a relatively larger hippocampus than the non-parasitic species. There were no sex differences in relative hippocampus size in screaming or bay-winged cowbirds, but female shiny cowbirds had a larger hippocampus than the male. |
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Instituto de Biologia y Medicina Experimental-CONICET, Buenos Aires, Argentina |
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English |
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0959-4965 |
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PMID:8730816 |
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Equine Behaviour @ team @ |
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4798 |
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Caraco, T.; Kacelnik, A.; Mesnick, N.; Smulewitz, M. |
| Title |
Short-term rate maximization when rewards and delays covary |
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Journal Article |
| Year |
1992 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
44 |
Issue |
Part 3 |
Pages |
441-447 |
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In nature foragers must exploit resources that vary randomly in both the energy acquired per item (reward) and the time required to pursue, capture and process an item (delay). Furthermore, rewards and delays associated with particular resources may often covary significantly. An analytical model asks how variance-covariance levels for rewards and delays could influence choice of resources when lack of information or cognitive limitation implies that a consumer attempts to maximize its short-term rate of energy gain. Both greater expected reward and reduced expected delay clearly should enhance preference for a resource. The model predicts that increased delay variance and reduced reward-delay covariance should increase a forager's preference for a resource. A forager should be risk-averse towards reward variance when the reward-delay covariance is positive, but should become risk-prone towards reward variance when the reward-delay covariance is negative. |
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2113 |
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Bateson, M.; Kacelnik, A. |
| Title |
Accuracy of memory for amount in the foraging starling,Sturnus vulgaris |
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Journal Article |
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1995 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
50 |
Issue |
2 |
Pages |
431-443 |
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Attempts to include psychological constraints in models of foraging behaviour differ in their assumptions concerning the accuracy of estimation of environmental parameters. Psychologists model estimation error as increasing linearly with the magnitude of a stimulus (Weber's Law), whereas behavioural ecologists either ignore error or assume it to be independent of stimulus magnitude. Studies on the estimation of time intervals have confirmed Weber's Law, but there are few data on the accuracy of estimation of amounts of food. Since the currency of most foraging models is the amount of food acquired per unit of time spent foraging, information on estimation of amount is required. Here, a titration method was used in which starlings chose between two cues. One colour signalled a standard food reward, and the other a reward that adjusted in magnitude according to the birds' choices: it increased when the standard was preferred and decreased when the adjusting option was preferred. There were two standards of 3 and 9 units of food, each of which was delivered at two rates to control for possible effects of rate of reinforcement on discrimination. The observed value of the adjusting option oscillated around a mean value slightly larger than that of the standard. The amplitude and period of these oscillations were larger when the standard was larger, independent of the rate of reinforcement. Also, molecular analysis showed that the probability of choosing the currently larger alternative increased as the relative difference between the adjusting option and standard increased. These results are consistent with Weber's Law applying to starlings' memories for amounts of food. |
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