A new effect of luminance gradient on achromatic simultaneous contrast

A new effect in the domain of achromatic simultaneous contrast has been observed. A middle gray region placed at the center of an area filled by a linear achromatic gradient from black (outer part) to white (inner part) is perceived as being much darker than an identical middle gray region surrounded by a reversed gradient. By using a matching task in two experiments, it has been shown that this phenomenon is much stronger than the classical achromatic simultaneous contrast effect. The new effect is interpreted in terms of thealbedo hypothesis.     

The simultaneous acquisition effect: simultaneous task learning inhibits memory for order

Delayed recall of a list of words learned simultaneously with other lists is superior to that of a list of words learned singly. A Brown-Peterson-like task was used to investigate this simultaneous acquisition effect from the perspective of the item-order distinction. It was hypothesized that simultaneous task learning would impede the encoding of order information but promote the encoding of item-specific information relative to single-task learning. The results of the first four experiments strongly supported the hypothesis that simultaneous task learning decreases the encoding of order information but provided no evidence that it facilitated the encoding of item-specific information. Additionally, Experiment 5 showed that the simultaneous acquisition effect did not occur in a mixed-list design, demonstrating an important boundary condition of the effect.     

Monitoring simultaneous auditory messages

If a S is asked to monitor two simultaneous auditory speech messages and to report only on the occurrence of target words appearing at random in either message, then it is shown that he witt fail to detect all of them but will detect significantly more than half. The targets used in these experiments were immediate repeats of text words. The results reject theories that part of the sensory input is blocked or that all is recognized. Detection performance was a function of rate of speech and of intertarget interval; there was a small, not significant, effect of instruction to recognize message content.     

A new method for solving simultaneous linear equations associated with multivariate analysis

A method is outlined whereby the equations resulting from multivariate analyses may be solved. Only the upper or lower triangular coefficient matrix need be employed. All solutions involving any combination(s) of the variables represented in the coefficient matrix are readily obtainable without permutation of the matrix. All solutions are given immediately without the need for back solving. One variable is added to or subtracted from the regression equation with each application of the method. The method may be applied as repeatedly as needed for any particular solution.     

Stimulus function in simultaneous discrimination

In discrimination learning, the negativity of the stimulus correlated with nonreinforcement (S-) declines after 100 training trials while the stimulus correlated with reinforcement (S+) is paradoxically more positive with lesser amounts of discrimination training. Training subjects on two simultaneous discrimination tasks revealed a within-subjects overlearning reversal effect, where a more-frequently presented discrimination problem was better learned in reversal than was a discrimination problem presented less frequently during training.     

Color-selectivity in simultaneous motion contrast

Thirty-two Ss were required to estimate the apparent motion of stationary vertical lines viewed against a background of moving vertical lines when both patterns were seen by the same eye (monoptic conditions) or the center pattern was seen by one eye and the surrounds by the other eye (dichoptic conditions). The stationary lines appeared to be moving from right to left as the surrounds moved left to right. The simultaneous motion contrast found under monoptic conditions was maximal when the center pattern and the surrounds were the same color and was reduced when they differed in color. The surrounds had limited influence on the apparent motion of the center section under dichoptic condition, and the color relationship was no longer important. Related color selectivity has been reported for the motion aftereffect (successive motion contrast), and both sets of data can be attributed to inlaibitory interaction (simultaneous in one case and successive in the other) among neural detectors tuned to wavelength as well as the direction of image motion.     

Successive responses to simultaneous stimuli

Previous work had shown that, when a memory-span experiment is performed with half the items presented to one ear, and half simultaneously to the other, a certain order of response appears. Either one ear or the other is dealt with first, and then the remaining items produce a response afterwards. The present results extend this finding to the eye and the ear rather than the two ears, and also to two voices distinguished by their frequency characteristics. For the latter condition, it is also shown that alternation of attention can take place at a speed faster than between the two ears. The effect thus appears to be a general one, and not merely a peculiarity of binaural hearing.     

Instructive feedback: A comparison of simultaneous and alternating presentation of non-target stimuli

Instructive feedback involves presenting extra, non-target stimuli in the consequent events for children's responses. Two methods of presenting instructive feedback during direct instruction were compared. These methods involved presenting two extra stimuli on all trials, and presenting the two extra stimuli separately on alternating trials. Preschool students were taught coin combinations using a constant time delay procedure with instructive feedback stimuli added to both praise and correction statements. An adapted alternating treatments design was used to evaluate the two methods of presenting instructive feedback. The students were assessed to determine the extent to which instructive feedback stimuli were learned. The results indicate that students learned some of the instructive feedback stimuli and no consistent differences in the effectiveness of the two presentation methods were noted. Further, relationships between the two instructive feedback stimuli appeared to be established. Implications for instruction and future research are discussed.     

Cerebral lateralization in simultaneous interpretation

Cerebral asymmetries for L1 (Italian), L2 (English), and L3 (French, German, Spanish, or Russian) were studied, by using a verbal-manual interference paradigm, in a group of Italian right-handed polyglot female students at the Scuola Superiore di Lingue Moderne per Interpreti e Traduttori (SSLM-School for Interpreters and Translators) of the University of Trieste and in a control group of right-handed monolingual female students at the Medical School of the University of Trieste. In an automatic speech production task no significant cerebral lateralization was found for the mother tongue (L1) either in the interpreting students or in the control group; the interpreting students were not significantly lateralized for the third language (L3), while weak left hemispheric lateralization was shown for L2. A significantly higher degree of verbal-manual interference was found for L1 than for L2 and L3. A significantly higher disruption rate occurred in the meaning-based mode of simultaneous interpretation (from L2 into L1 and vice versa) than in the word-for-word mode (from L2 into L1 and vice versa). No significant overall or hemispheric differences were found during simultaneous interpretation from L1 into L2 or from L2 into L1.     

Interaction of simultaneous visual events

Five experiments are reported in which a perceptual interaction between simultaneous brief events was investigated. Subjects judged whether a briefly presented stimulus was flickering or not. Performance was much more error prone when a similar unattended stimulus was presented at a relatively remote position in the visual field, thus confirming previous findings. Interference was obtained for stimuli presented both peripherally and centrally in the visual field. The effect was not confined to large stimuli, but the larger the interfering stimulus the greater the effect it had. Events in the auditory modality interfered with judgements made in the visual modality. Possible mechanisms for the interaction are discussed.     

The solution of simultaneous equations

This paper is an attempt to integrate the various methods which have been developed for the numerical solution of simultaneous linear equations. It is demonstrated that many of the common methods, including the Doolittle Method, are variations of the method of single division. The most useful variation of this method, in case symmetry is present, appears to be the Abbreviated Doolittle method. The method of multiplication and subtraction likewise can be abbreviated in various ways of which the most satisfactory form appears to be the new Compact method. These methods are then applied to such problems as the solution of related equations, the solution of groups of equations, and the evaluation of the inverse of a matrix.     

Peripheral viewing and simultaneous contrast

An experiment was done to find the effect on simultaneous brightness contrast of viewing the test patches foveally or peripherally, at a distance of 3° or 6° from the fovea. It was found that contrast was greater in the periphery. It was also found that contrast increased with prolonged viewing of the display. A further experiment showed that blurring the test patches produced an increase in contrast.     

Depth adjacency in simultaneous contrast

The Gelb phenomenon, as an example of whiteness contrast, was investigated with three amounts of separation in depth between the test and induction disc. The cue of binocular disparity was used to vary the perceived depth between the discs. It was found that the magnitude of the contrast effect decreased with an increase in the perceived depth between the two discs. This change was regarded as an instance of the adjacency principle. The problem of whether the binocular disparity cue per se or perceived depth was the significant variable was discussed. The consequences of the results were considered with respect to the relation between whiteness constancy and whiteness contrast and the problem of neural localization of the contrast effect.     

A new device to present textured stimuli to touch with simultaneous EEG recording

The study of touch has recently grown, due mainly to the extensive use of several types of actuators that stimulate several subsystems of touch. There is a widespread interest in applying these mechanisms to the study of the neurophysiological correlates of tactual perception. In this article, we present a new device (the tactile spinning wheel [TSW]) for delivering textured surfaces to the finger pad. The TSW allows one to control several parameters of the stimulation (angular speed, texture, etc.) and, connected to an EEG recording system, makes it possible to study neural electrophysiological events. The device consists of a rotating platform on which the tactile stimuli are fixed, a system that synchronizes stimuli onset with the EEG system, and an electronic interface that controls the platform. We present the technical details of the TSW, its calibration, and some experimental results we have obtained with this device.