Biomedical subjects

M S Dawkins

Publications and source records attributed to M S Dawkins.

7 recordsLinked to original sources

PubMed2000

Pattern recognition and active vision in chickens.

Recognition of objects or environmental landmarks is problematic because appearance can vary widely depending on illumination, viewing distance, angle of view and so on. Storing a separate image or 'template' for every possible view requires vast numbers to be stored and scanned, has a high probability of recognition error and appears not to be the solution adopted by primates. However, some invertebrate template matching systems can achieve recognition by 'active vision' in which the animal's own behaviour is used to achieve a fit between template and object, for example by repeatedly following a set path. Recognition is thus limited to views from the set path but achieved with a minimal number of templates. Here we report the first evidence of similar active vision in a bird, in the form of locomotion and individually distinct head movements that give the eyes a similar series of views on different occasions. The hens' ability to recognize objects is also found to decrease when their normal paths are altered.

Animals↗

PubMed1998

Evolution and animal welfare.

Animal welfare is a topic often thought to reside outside mainstream biology. The complexity of the methods used to assess welfare (such as health, physiology, immunological state, and behavior) require an understanding of a wide range of biological phenomena. Furthermore, the "welfare" of an animal provides a framework in which a diversity of its responses can be understood as fitness-enhancing mechanisms. Different methods for assessing animal welfare are discussed, with particular emphasis on the role of an animal's own choices and reinforcement mechanisms. No part of biology is as yet able to explain consciousness, but by confronting the possibility that nonhuman animals have conscious experienced of suffering, animal welfare studies force a consideration of even this hardest problem of all biological phenomena in a particularly direct and evolutionary way.

Animal Welfare↗

PubMed1995

An exaggerated preference for simple neural network models of signal evolution?

Recently, simple neural network models have been used to explain the evolution of important phenomena in animal signalling, such as extravagant ornamentation and symmetrical signals, as responses to inevitable 'hidden preferences' of recognition systems. We argue that these very simple models may be misleading because they may not behave in important ways like the recognition systems of real animals and so cannot justify their claim to demonstrate general principles of perception in a signalling context. We show that the way in which these simple models respond to exaggerated signals may not be, as is claimed, a close parallel to the phenomena of peak shift or supernormal responses. We also argue that the preference for symmetrical patterns shown by the models is unlikely to reflect the way computationally that real animals solve problems of pattern invariance and may be an artefact of the particular way the models have been set up. Whereas more sophisticated neural net models do capture known properties of real visual systems and are consequently of great use in understanding perception, the same cannot be said of very simple one-dimensional models with small numbers of units and connections. Given the far reaching explanatory claims made of these simpler models their limitations should be more widely recognized.

Animal Communication↗

PubMed1993

Are there general principles of signal design?

Explanations of signal design must meet three requirements: they must be logically coherent, they must explain the diversity in size of animal signals and they must explain the diversity in form of signals. Three selection pressures operating on animal signals are discussed: the degree of conflict or cooperation, the 'efficacy' of signals and how signalling costs are paid. A distinction is made between cases where costs of signalling are paid in the production of the signal and cases where costs are paid as a consequence of giving a signal on the grounds that differences in signal design result. This is illustrated by reference to the example of warning coloration. It is concluded that general principles still elude us because of the numbers of different selection pressures that operate on the design of animal signals.

Animal Communication↗

PubMed1993

Receiver psychology and the design of animal signals.

Animal communication is studied both by neurobiologists and by evolutionary biologists, but in very different ways. The purpose of this article is to show how both groups could benefit from a greater appreciation of each other's approach. Evolutionary biologists should take more account of the role played by the sensory systems and brains of receivers in constraining the design of animal signals. Neurobiologists should be more aware of recent advances in the understanding of signal-receiver co-evolution and the evolutionary origins of animal signals. A series of recent examples are cited that illustrate how pre-existing neurophysiological or psychological properties of receiver organisms are essential to our understanding of the design characteristics of animal signals and of their origins. Also discussed are a number of other areas of signalling in which the study of 'receiver psychology' is likely to be fruitful.

Animal Communication↗

PubMed1985

Cage height preference and use in battery-kept hens.

Caged hens are shown to have a strong preference for cages which have a large vertical space allowance. When filmed in cages of unrestricted head room, nearly 25 per cent of hens' head movements occurred above 40 cm, which is the proposed CEC recommendation.

Animals↗

PubMed1983

Cage size and flooring preferences in litter-reared and cage-reared hens.

Pullets (Ross Rangers) reared commercially either in cages or on deep litter were tested for their responses to small (0.38 X 0.43 m) and large (0.76 X 0.86 m) cages with wire floors and to small and large cages with litter floors. When tested at 29 weeks of age, the birds' responses were significantly affected both by cage size (large preferred to small) and by flooring (litter preferred to wire). No difference in cage preference was apparent between cage-reared and litter-reared birds either when they were first tested at 17 weeks or when they were re-tested at 29 weeks. Birds do not have to be reared on litter in order to be attracted by it.

Animals↗