On the confounding effects of phosphor persistence in oscilloscopic displays.

Phosphor persistence has been a source of confounding in studies of temporal integration in vision. We examined the confounding by assessing the effects of the persistence of two commonly-used phosphors (P15 and P31) on performance of a temporal-integration task. In one experiment we eliminated the visibility of phosphor persistence by closing two mechanical shutters upon display termination. In a second experiment we estimated the duration of phosphor persistence by displaying the image behind closed shutters which opened upon display termination. No detectable persistence was every produced by P15 phosphor. By contrast, P31 phosphor produced persistence that lasted several hundred milliseconds even when a veiling light was projected on the screen. We ascribe the earlier instances of confounding to inadequate interpretation of the technical data on phosphor decay.

Attention and eye movement control: an overview.

A review of recent experimental and theoretical findings is presented which relates the results of neurophysiological and psychological research on attention and eye movement to cognitive theorizing. With respect to the relation between shifts of attention and saccadic eye movements, several experiments have demonstrated that it is possible to dissociate the line of attention from the gaze direction. On the other hand, there is some indirect (although not yet conclusive) evidence that saccadic eye movements always produce a concomitant shift of attention. Another question is whether there is a moment-to-moment control of each consecutive saccade and latency or whether indirect control models (i.e. planning several saccades in advance) are more appropriate. The function of attentional processes which have to coordinate stimulus driven (bottom-up) and concept driven (top-down) mechanisms are discussed and related to some studies investigating local and global scanpaths.

A model of visible persistence and temporal integration.

A quantitative model of temporal integration and visible persistence is described and tested. The model treats visible persistence as resulting from processing activity within sustained visual channels whose temporal response is modelled using a second-order control system. Temporal integration of two successive stimuli is assumed to be enabled by the overlap between the two periods of activity and to be impaired by the non-overlapping activity. The model successfully predicts the effects of inter-stimulus interval and of stimulus duration on goodness of temporal integration.