Marina T. Groner

Attention and eye movement control: an overview

SummaryA 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.

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.

Beyond the displacement limit: An analysis of short-range processes in apparent motion

If a circle of random dots is presented in two successive displays in which the second is rotated in relation to the first, then observers are able to accurately discriminate the direction of apparent rotation as long as the rotation is small. Rotations beyond this short-range apparent motion can produce the impression of motion in the reverse direction. The performance in identifying the direction of rotation further depends on the eccentricity of stimulation and the density of the random dots. Simulations of the experiments using the Marr and Ullman model of motion detection are in good quantitative agreement with the data except for low dot density patterns and large displacements. In these situations perception seems to be dominated by the operation of long-range processes.

Kurz-, mittel- und längerfristige Effekte eines Trainings in phonologischer Bewusstheit und in Buchstaben-Laut-Korrespondenz auf die phonologische Bewusstheit und die Lese- und Rechtschreibleistung

Zusammenfassung: Fragestellung: Die vorliegende Studie hatte zum Ziel, die kurz, mittel- und langerfristige Wirksamkeit eines vorschulischen Trainings in phonologischer Bewusstheit und in Buchstaben-Laut-Korrespondenz, durchgefuhrt in Schweizer Mundart an einer Schweizer Stichprobe, an Hand der Outcomevariablen phonologische Bewusstheit und Lese- und Rechtschreibleistungen zu uberprufen. Methodik: Aus insgesamt 109 Kindern mit vollstandigen Datensatzen uber den Erhebungszeitraum wurde fur die statistischen Analysen eine gepaarte Stichprobe aus je 26 Kindern aus Experimental- und Kontrollgruppe extrahiert. Es wurden einerseits Effekte des Trainings auf die kurz, mittel- und langerfristige Entwicklung der phonologischen Bewusstheit untersucht, andererseits die mittleren Lese- und Rechtschreibleistungen von Trainings- und Kontrollgruppe sowie der Anteil an lese- und rechtschreibschwachen Kindern in den jeweiligen Gruppen am Ende des 1. und 2. Schuljahres verglichen. Ergebnisse: Effekte des Trainings auf die ...

The Role of Heuristics in Models of Decision

Publisher Summary This chapter discusses the role of heuristics in the models of decision. Artificial Intelligence comprises all efforts at making computers solve problems that require intelligence, such as playing chess, proving logical theorems, making medical diagnoses, designing and analyzing electronic circuits, and understanding language or images. Artificial Intelligence can be seen from two different viewpoints, from engineering point of view and from a scientists point of view. From an engineering point of view, its goal is to produce machines that are increasingly powerful in increasingly diverse areas of application. From the second, more general point of view, Artificial Intelligence is a new approach to determine the prerequisites of intelligent behavior and to uncover its nature, independent of whether this behavior is produced by a natural, biological, or an artificial system.

Phosphor persistence in oscilloscopic displays: Its luminance and visibility.

Phosphor persistence and its potentially confounding effects in visual experiments were discussed recently in these pages (Groner, Groner, Miiller, Bischof & Di Lollo, 1993). In that report, we showed that phosphor persistence can remain visible for extended periods (in the order of hundreds of msec) on oscilloscopic screens coated with P31 but not with P15 phosphor. In a dissenting research note, Westheimer (1993) dismisses our evidence as stemming from “very indirect exper- iments” and concludes that the persistence of P31 phos- phor, as measured by a photometer, decays within about 2 msec. This 2-msec estimate could be easily taken as applying equally to photometers and to human observ- ers. To obviate this misinterpretation, the generality of Westheimer’s conclusion needs to be qualified. A common reason for measuring the temporal course of phosphor decay is to provide engineering specifica- tions for display oscilloscopes (e.g. Bell, 1970). For this purpose, the measuring instrument of choice is a photo- meter, not the human eye. As pointedly noted by Westheimer (1993), human eyes would supply only indirect estimates. We agree: instead of the direct lumi- nance readings provided by a photometer, visual re- sponses yield only