Visual stimuli

For the central measurement, the field of view is rectangular (e.g., 0.3 by 1.25°) and for other eccentricities, the field is an annular arc similar to that provided in minimum motion photometry. The use of a CRT monitor introduces the same problem as the use of LEDs in HFP, namely, the broadband nature of the screen phosphors, and a correction must be made before reporting the peak MP optical density. A system that could employ lamps and filters instead of a CRT monitor would be difficult to design because of the complexity of the visual stimulus. 

J. H. Meek, C. E. Elwell, M. J. Khan, J. Romaya, J. D. Wyatt, D. T. Delpy, and S. Zeki. Regional changes in cerebral hemodynamics as a result of a visual stimulus measured by near infrared spectroscopy. Proceedings of Royal Society of London, 261 351-356, 1995. 

Visual stimulus of fleeing facilitates flight of whole group... 

Subjective states were also monitored regularly in the footballers over the 71 hr. The data in Figure la illustrate how anxiety increased with successive nights of sleep deprivation. The influence of a circadian subharmonic in the observations is also obvious. Unprepared reaction time, recorded on each participant regularly through the entire period, deteriorated in phase with subjective states (Fig. lb). Prolonged gaps in attention, when the subject failed to respond at all to the visual stimulus, were excluded from the data. 

A recently developed technique for infant assessment is embodied in the Fagan Test of Infant Intelligence, which assesses visual recognition memory. In this test, an infant faces a display with two screens. On one screen, a visual stimulus is presented for a specified period of time. Subsequently, that visual stimulus is projected on one screen and, at the same time, another visual stimulus is projected onto another screen. An observer records the amount of time the infant spends gazing at each screen. Normal infants look away from the visual stimulus which they have already seen and spend more time gazing at the novel stimulus, a trait which has been shown to correlate with higher scores later in development on the Stanford-Binet intelligence test. 

Infant performance on a test of novelty preference has also been related to later intellectual ability. In these studies attention to a novel visual stimulus is measured... 

Note that brightness is a subjective (mental) response to a visual stimulus. Brightness, for points of light against a dark background, is approximately a logarithmic response to light intensity. 

This investigation measures the latency of response to a visual stimulus, usually a light flash or a changing checkerboard pattern. It evaluates the conductive function of the anterior visual pathways, particularly the optic nerves. 

What is the function of courtship display and courtship stationary paddling It is probably a multimodal signal to females. It probably contains a visual signal, since sexually receptive females respond to a model of a male crab in the stationary posture of courtship display (Teytaud 1971) and the red color on the female claws can induce courtship by males (Baldwin and Johnsen 2009). The dynamic component of the display, paddling, probably also provides a characteristic and conspicuous visual stimulus, though this has not been experimentally tested. The water current generated... 

FIGURE 6.22.6 Drawings made by patients after stroke damage to one brain hemisphere or the other. The visual stimulus is on the left. In the middle is what is seen by the left hemisphere, and on the right is what is seen by the right hemisphere. (From Robertson, L.C., Phi Kappa Phi Forum, 85, 19, 2005. With permission.)... 

An approach sometimes used in a variety of measurement contexts incorporates a dual-task or divided attention scenario that is designed to require use of attention resources in two different simultaneously executed tasks [e.g., Wickens, 1984]. For example, visual tracking (primary task) accuracy and speed of response to an embedded visual stimulus (secondary task) can be measured. Details of the potential timesharing possibilities at play are quite complex [Schneider and Shiffrin, 1977 Shiffrin and Schneider, 1977]. 

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