A Woodington | PubMed Health

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↗

PubMed1997

Distance and the presentation of visual stimuli to birds

Artificial visual stimuli in the form of photographs, video sequences and computer-generated images are increasingly being used to explore the visual world of birds but their use is controversial as it is still not clear whether birds see them in the same way that humans do. While differences between bird and human colour vision may be one problem with using such artificial images, another and potentially even more important difficulty is the distance at which stimuli are presented. An experiment is described in which hens, Gallus gallus domesticuswere trained to move towards one of two real objects viewed at two different distances. Even for real objects, discrimination levels were better when the hens were allowed to view the stimuli from 5-25 cm than when they were forced to choose at 120 cm and this correlated with their ability to transfer to photographs of the same objects at different distances. In a colour discrimination at a short distance, five out of seven hens showed 100% correct responses when first shown photographs of real objects that they had previously learnt to discriminate. The results suggest that photographs can be used as substitutes for real stimuli but that care should be taken over the distance at which they are presented. The results are discussed in relation to the visual behaviour of birds and differences in functioning of their frontal and lateral visual fields.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗