Visual search and selection of natural stimuli in the pigeon: The attention threshold hypothesis.

Abstract

During visual search for samples of varying proportions of familiar, natural food grains displayed against a complex gravel background, pigeons exhibited "matching selection," a tendency to overselect the more common grain. The matchingselection effect was decreased at low levels of stimulus/background contrast and reversed when the grains were highly conspicuous. The results were consistent with the hypothesis that stimulus detectability should be enhanced by recent experience with a particular grain type, but they showed no convincing indications of a corresponding effect on the response criterion. An explanatory model, termed the attention threshold hypothesis, argues that the mean latency of discovery can be minimized by selectively attending to one stimulus type at a time and switching to a more generally receptive state when the rate of discovery falls below a threshold value. The model appears to account for the fact that the response rate was highest toward samples containing a single grain type and decreased as the relative proportions approached equality. Additional consequences of the adoption of this theoretical perspective were explored in some detail. Among other results, the evidence suggests that the switching threshold might be chosen so as to optimize the rate of food discovery.Animals that are ecological generalists, that is, apimals that forage for a variety of food, commonly exhibit a selection bias that depends on relative frequency (Curio, 1976;Krebs, 1973). Food types uncommon in the environment tend to be disproportionately underrepresented in the diet, whereas more abundant foods are consumed in excess. A selection bias could result from a number of passive factors, such as heterogeneity in the spatial distribution of food types or changes in food accessibility with density (Murdoch & Oaten, 1974). In animals that conduct a visual search for food, however, Tinbergen (1960) hypothesized that the bias may be attributable to active processes. Recent expe-I wish to thank D.

Evolutionary consequences of a search image

“…In contrast, search images have been proven to exist in a large range of predators (Tinbergen, 1960;Pietrewicz and Kamil, 1979;Bond, 1983;Melcer and Chiszar, 1989;Allen et al, 1998;Jackson and Li, 2004;Bond and Kamil, 2006). A possible explanation would be that in real systems predators are unable to completely control the prey densities, due to temporal and spatial heterogeneity in the environment, prey variability, multiple predator species etc.…”

“…Although the formation of a search image has historically been associated with bird species (Tinbergen, 1960;Pietrewicz and Kamil, 1979;Bond, 1983;Allen et al, 1998;Bond and Kamil, 2006), there is a strong indication that predators from different classes form search images. For example, Jackson and Li (2004) showed that hunting spiders also form search images.…”

“…This is called the formation of a search image by a predator (Tinbergen, 1960) and is related to apostatic selection (Bond, 2007). Research shows that a predator can only form a search image for one prey type at a time and this causes other prey types to be detected less frequently (Pietrewicz and Kamil, 1981;Bond, 1983;Gendron, 1986;Bond, 2007).…”

Odd-item search by pigeons: Method, instrumentation, and uses

“…M. Blough, 1984;Bond, 1983;Pietrewicz & Kamil, 1979). The odd-item method may also be useful in such research, as contrasts between odd-item and other data already suggest.…”

Adaptive foraging does not always lead to more complex food webs

“…Hence, the matrix A sets the structural 20 constraints on the food web (e.g., to avoid herbivores to feed on carnivores etc. will call this model the search image model; see also Bond (1983). The second model we use…”