Ken Goryo

Binocular, Monocular and Dichoptic Pattern Masking

It has been reported that a quadratic summation rule can account for threshold versus masker contrast (TvC) functions for binocular, monocular and dichoptic masking. However, the present study suggests that inputs from two eyes are summed in different ways. Foley’s model was revised to describe TvC functions for binocular, monocular and dichoptic masking. The revised model has the following two characteristics. First, the revised model receives two monocular inputs. Secondly, excitations and inhibitory signals are subjected to nonlinear transducer functions before and after summation of the monocular signals. A two-alternative forced-choice procedure was used to measure contrast thresholds for Gaussian windowed sine-wave gratings (target) in the presence of sine-wave gratings (masker). Thresholds were measured for 11 masker contrasts and the three masking conditions. It was shown that this revised model fitted the data resonably well. The revised model indicates how monocular inputs are summed in contrast processing.

Selective Looking and the Müller-Lyer Illusion: The Effect of Changes in the Focus of Attention on the Müller-Lyer Illusion:

According to a selective looking paradigm subjects were required to attend to the inward-going or outward-going components of a combined Müller-Lyer figure in which both components were present and distinguishable by colour. The amount of the illusion was found to vary according to which component the subject attended. Subsidiary findings relate the amount of the illusion to fin angle, fin length, and length of shaft.

PERCEPTUAL LEARNING IN VISUAL BACKWARD PATTERN MASKING

The present study examined the practice effect of backward pattern masking in the context of recent researches on perceptual learning. On the discrimination task, thresholds decreased substantially with practice. In addition, the practice effect was specific to the mask pattern. In contrast, it cannot reasonably be assumed that the practice effect was specific to the eye and the retinal position. These findings suggest that practice diminished the interruption of processing in capacity-limited processing. In addition, the specificity of the practice effect to the mask pattern suggests that participants learned to filter out the specific type of mask from capacity-limited processing. On the detection task, thresholds decreased with practice. But the improvement was smaller on the detection task than on the discrimination task. It may be assumed that the practice effect on the detection task does not involve a decrease in the effect of the interruption in capacity-limited processing.

Biscriptal interference: A study of english and japanese

It was once assumed that alphabetic, syllabic, and logographic scripts could be clearly differentiated in terms of their respective processing demands, but recent evidence suggests that, as visual stimuli, they all draw upon common “configurational” processing resources. Two experiments are reported which address this issue. Both employ cross-lingual interference paradigms, with the rationale that competition for limited processing resources will be reflected in the degree of interference generated when two scripts are presented simultaneously. The experiments differ in terms of task requirements, the first being a word-naming task, biased towards reliance upon the more rule-based decoding skills; whereas the second is a colour naming task, with a more configurational bias. In the first study, the locus of the interference effect was clearly pre-lexical, and interference was only generated by those scripts that could feasibly draw upon grapheme-phoneme correspondence rules. No interference was generated by logographs that could be accessed “directly” without recourse to any prelexical phonological code. In the second study, the locus of interference was twofold: early in processing, as a result of competition for configurational processes, and later, phonological output competition prior to articulation. These results clearly demonstrate major differences in the ways in which logographic, syllabic, and alphabetic scripts are processed.

Perceptual learning in monocular pattern masking: experiments and explanations by the twin summation gain control model of contrast processing.

We investigated practice effects on contrast thresholds for target patterns. Results showed that practice decreased contrast thresholds when targets were presented on maskers. Thresholds tended to decrease more at the higher end of the masker contrast range. At least partially, learning transferred to stimuli of the untrained phase. We simulated changes in threshold versus contrast functions using a contrast-processing model and then fit the model to pre- and posttraining data. The simulation results and model fit suggest that learning in pattern masking can be accounted for by changes in nonlinear transducer functions for divisive inhibitory signals.

Attenuation of the pupillary response to luminance and color changes during interocular suppression

The present study investigated the effects of interocular suppression on the pupillary constriction to luminance and color changes. Stable interocular suppression was produced by presenting a flickering high-contrast grating to one eye and a spatially homogeneous field to the other eye. The results showed that the pupillary responses to luminance as well as color changes were clearly attenuated during interocular suppression; the pupillary constriction to stimulus changes was delayed and reduced in amplitude when those changes occurred in the suppressed eye. The attenuation of the pupillary response was observed over a wide range of test contrast extending to well above the threshold level. Moreover, the properties of the suppressive effect were very similar to those assessed psychophysically using both detection thresholds for weak stimuli and reaction times for suprathreshold stimuli. Overall, the present study provided converging evidence that the pupillary response can be a useful objective probe of interocular suppression in humans. The results are discussed in view of possible differential involvements of subcortical and cortical visual processing in driving the pupillary response as well as in interocular suppression.

Eye- and feature-based modulation of onset rivalry caused by the preceding stimulus

Pre-exposure to a stimulus can modulate initial perceptual dominance experienced in binocular rivalry with brief test stimuli (onset rivalry). This study investigated this modulating effect using both color and pattern stimuli. We confirmed separate contributions of eye- and feature-based suppressions and showed that their relative strength varied with temporal parameters. Eye-based suppression was stronger with a short test duration (10 ms) and shorter ISIs between the preceding and test stimuli. On the other hand, feature-based suppression grew with ISI and was more pronounced with a longer test duration (200 ms). We also investigated the nature of the modulating effect associated with feature-based suppression using chromatic gratings of high luminance contrast. Results revealed that different features of the preceding stimulus (i.e., color and orientation) exerted nearly independent effects on onset rivalry. However, different features shared their fate in competitive interactions for perceptual dominance; when one feature became dominant, the other also dominated. These findings suggest that competitive interactions for perceptual dominance and the modulation of these interactions are mediated at least partially by different mechanisms. Overall, the present findings are consistent with a theoretical view that initial dominance is established through competitive interactions at multiple levels of processing.

Rapid proportion comparison with spatial arrays of frequently used meaningful visual symbols

It has been shown that when two arrays of Arabic numerals were briefly presented, observers could accurately indicate which array contained the larger number of a target numeral. This study investigated whether this rapid proportion comparison can be extended to other meaningful symbols that share some of notable properties of Arabic numerals. We tested mainly several Japanese Kanji letters, each of which represents a meaning and can work as a word. Using physically identical stimulus sets that could be interpreted as different types of letters, Experiment 1 first confirmed the rapid proportion comparison with Arabic numerals for Japanese participants. Experiment 2 showed that the rapid proportion comparison can be extended to Kanji numerals. Experiment 3 successfully demonstrated that rapid proportion judgments can be found with non-quantitative Kanji letters that are used frequently. Experiment 4 further demonstrated the rapid proportion comparison with frequently used meaningful non-letter symbols (gender icons). The rapid processing cannot be attributed to fluent processing of familiar items, because it was not found with familiar phonograms (Japanese Kana letters). These findings suggest that the rapid proportion comparison can be commonly found with frequently used meaningful symbols, even though their meaning is not relevant to the task.