The Role of Attention in Ambiguous Reversals of Structure-From-Motion

Multiple dots moving independently back and forth on a flat screen induce a compelling illusion of a sphere rotating in depth (structure-from-motion). If all dots simultaneously reverse their direction of motion, two perceptual outcomes are possible: either the illusory rotation reverses as well (and the illusory depth of each dot is maintained), or the illusory rotation is maintained (but the illusory depth of each dot reverses). We investigated the role of attention in these ambiguous reversals. Greater availability of attention – as manipulated with a concurrent task or inferred from eye movement statistics – shifted the balance in favor of reversing illusory rotation (rather than depth). On the other hand, volitional control over illusory reversals was limited and did not depend on tracking individual dots during the direction reversal. Finally, display properties strongly influenced ambiguous reversals. Any asymmetries between ‘front’ and ‘back’ surfaces – created either on purpose by coloring or accidentally by random dot placement – also shifted the balance in favor of reversing illusory rotation (rather than depth). We conclude that the outcome of ambiguous reversals depends on attention, specifically on attention to the illusory sphere and its surface irregularities, but not on attentive tracking of individual surface dots

The optokinetic response in wild type and white zebra finches

Eckmeier D, Bischof H-J. The optokinetic response in wild type and white zebra finches. Journal of Comparative Physiology, A: Neuroethology Sensory Neural and Behavioral Physiology. 2008;194(10):871-878.Optic flow is a main source of information about self movement and the three-dimensional composition of the environment during locomotion. It is processed by the accessory optic system in all vertebrates. The optokinetic response is elicited by rotational optic flow, e.g. in a rotating drum lined with vertical stripes. We investigated here the effect of rotational optic flow on the optokinetic response in wild type and white zebra finches. The highest stimulus velocity eliciting an optokinetic response (upper velocity threshold) was dependent on stimulus direction and illumination level, but was not different between the colour morphs. The upper velocity threshold was higher with temporal to nasal movements in monocularly exposed birds and symmetrical with binocular exposure. Its increase with illumination level followed Fechner's law and reached a plateau at about 560 Lux. In bright daylight, white birds did not show optokinetic responses. We conclude that the altered wiring of the visual system of white birds has no influence on accessory optic system function. The unwillingness of white birds to respond with optokinetic response in bright daylight may be due to a substantial lack of inhibition within the visual system as demonstrated earlier, which may enhance the sensibility to glare

Feminist narrative research: opportunities and challenges

In this chapter I discuss narrative frameworks and dominant narratives. I argue for the need to go beyond the story as told to explore how and why we come to tell particular stories—often in the context of limited alternatives—and in doing so identify some of the difficulties for feminists in interrogating women’s stories. I draw on my own research on women’s engagement with narratives of childhood sexual abuse to explore how and why women might draw on such a narrative framework to construct themselves as damaged and responsible for their own unhappiness, often with no concrete memories on which to base their stories. In identifying some of the limitations of (telling) particular damage narratives the chapter also serves as a cautionary tale of the dangers of contemporary stories