Visual evoked potentials related to behavioral asymmetries during foveal attention in the two extrapersonal Hemispaces

In a group of male and female subjects we studied the VEPs related to the solution of a lexical decision task presented in the Left and Right Hemispaces with respect to the Central position in order to explore the electrophysiological correlates of the performance asymmetries obtained when overt spatial attention is directed to the Left or Right Hemispace. When stimuli were presented in the Left Hemispace a significant asymmetry was observed between the two hemispheres of the negative activity around 280 msec in the occipital-parietal areas. Moreover a general increase in the Central and Frontal areas of both the hemispheres was observed. In this paper we discuss why these effects can be considered to be the cause of the costs on accuracy observed in the male subjects. The differences obtained with the female group are discussed in relation to the observed modification on the negative activity around 400 msec with stimuli in the Left Hemispace. These findings give some suggestions about the interaction of structural and attentional mechanisms in the brain during the solution of a lateralized cognitive task.     

CHROMATIC ROD VISION III. Duration of pre-stimulation varied

S tabell B. & S tabell U. Chromatic rod vision. III. Duration of pre-stimulation varied. Scand. J. Psychol ., 1972, 13 , 136–140.—The scotopic contrast hue was determined as a function of duration of pre-stimulation, together with the additive opponent hue. It is concluded that the red/blue ratio which has to be added to the additive opponent hue to produce the scotopic contrast hue, may change as a function of both wavelength and duration of pre-stimulation.     

CHROMATIC ROD VISION

S tabell B. & S tabell U. Chromatic rod vision. IV. Time between pre-and test-stimulation varied. Scand. J. Psychol ., 1972, 13 , 141–144.—The scotopic contrast hue was determined as a function of time between pre-and test-stimulation. As the interval increased, the scotopic hue was found to change from orange toward yellow in the 440–475 nm region of pre-stimulation and from violet-blue toward violet in the 550–595 nm region. It is concluded that (1) depending on wavelength of pre-stimulation, the processes in the red-green substance may revert to the mid-valued state faster or slower than the processes in the yellow-blue substance, and (2) the red/blue ratio of the violet hue which has to be added to the additive opponent hue to produce the scotopic contrast hue, may change as a function of time between pre- and test-stimulation.     

TRANSITION FROM ROD TO CONE VISION:III. Successive contrast anew

S tabell , U. & S tabell , B. Transition from rod to cone vision. III. Successive contrast anew. Scand. J. Psychol ., 1969, 10 , 140–144—The relation between the specific threshold level and the upper limit of the scotopic contrast color was investigated. The achromatic interval between the scotopic and the photopic component increased when time in darkness increased, and when pre-stimulation was reduced as regards intensity, duration, or cone/rod ratio. The results are interpreted on the basis of the opponent theory of color vision.     

On the scaling of visual space from motion—in response to Pizlo and Salacfa-Golyska

Pizlo and Salack-Golyska (1994) have raised an important question about the validity of the interpretation of experiments reported by Lappin and Love (1992)—based on the fact that alternative cues in the image plane might have supported the shape discriminations in those experiments. The meaning of the hypothesis that visual space may be scaled by congruence under motion is clarified, pertinent evidence is reviewed, and new experimental evidence is reported We conclude that visual space can be metrically scaled by congruence of moving shapes.     

The polyserial correlation coefficient

The polyserial and point polyserial correlations are discussed as generalizations of the biserial and point biserial correlations. The relationship between the polyserial and point polyserial correlation is derived. The maximum likelihood estimator of the polyserial correlation is compared with a two-step estimator and with a computationally convenient ad hoc estimator. All three estimators perform reasonably well in a Monte Carlo simulation. Some practical applications of the polyserial correlation are described.By coincidence, the first author and the second and third authors learned that they were working independently on closely related problems and, consequently, decided to write a jointly authored paper.