The centroid paradigm: Quantifying feature-based attention in terms of attention filters

This paper elaborates a recent conceptualization of feature-based attention in terms of attention filters (Drew et al., Journal of Vision, 10(10:20), 1-16, 2010) into a general purpose centroid-estimation paradigm for studying feature-based attention. An attention filter is a brain process, initiated by a participant in the context of a task requiring feature-based attention, which operates broadly across space to modulate the relative effectiveness with which different features in the retinal input influence performance. This paper describes an empirical method for quantitatively measuring attention filters. The method uses a "statistical summary representation" (SSR) task in which the participant strives to mouse-click the centroid of a briefly flashed cloud composed of items of different types (e.g., dots of different luminances or sizes), weighting some types of items more strongly than others. In different attention conditions, the target weights for different item types in the centroid task are varied. The actual weights exerted on the participant's responses by different item types in any given attention condition are derived by simple linear regression. Because, on each trial, the centroid paradigm obtains information about the relative effectiveness of all the features in the display, both target and distractor features, and because the participant's response is a continuous variable in each of two dimensions (versus a simple binary choice as in most previous paradigms), it is remarkably powerful. The number of trials required to estimate an attention filter is an order of magnitude fewer than the number required to investigate much simpler concepts in typical psychophysical attention paradigms

Nutrition and lactational control of fertility in red deer

In many mammals, including man, lactation is associated with a delay in return of fertility. The pattern of suckling activity, particularly suckling frequency, is known to be important in determining the length of this anovulatory phase1,2. In a seasonally breeding ungulate such as red deer, lactation coincides with a photoperiodically controlled period of seasonal anoestrus3. Nevertheless, lactation may still exert an important effect on the duration of infertility as lactating red deer hinds on poor quality hill pasture resume oestrus at a later date than non-lactating hinds and frequently fail to ovulate in the year following the birth of a calf 4,5. It has been proposed that this reproductive failure is due to the effect of both lactation and poor planes of nutrition on maternal body condition6-8. As a result of our recent studies on the influence of plane of nutrition on milk yield and suckling behaviour in red deer we now propose an alternative hypothesis. We suggest that the principal influence of low planes of nutrition is to increase the suckling frequency of the calf in response to a decrease in availability of milk. It is this increase in suckling frequency, and perhaps the associated increase in plasma levels of prolactin, which is the major determinant of the reproductive failure and is due to the influence of plane of nutrition on the production of milk by the mother rather than on maternal body condition. This hypothesis may have important implications for our understanding of the role of nutrition in determining the length of lactational infertility in many species including man. © 1983 Nature Publishing Group