メタコントラストのマスキング関数を規定する要因についての研究 刺激のエネルギー関係の効果

丸山 規明; 内山 道明

doi:10.4992/jjpsy.51.318

A STUDY ON THE FACTORS DETERMINING THE MASKING FUNCTION OF METACONTRAST

EFFCT OF ENERGY RELATION IN STIMULI

NORIAKI MARUYAMA, MICHIAKI UCHIYAMA

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JOURNAL FREE ACCESS

1981 Volume 51 Issue 6 Pages 318-326

DOI https://doi.org/10.4992/jjpsy.51.318

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Published: March 20, 1981 Received: March 24, 1980 Available on J-STAGE: July 16, 2010 Accepted: - Advance online publication: - Revised: -
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Date of correction: July 16, 2010 Reason for correction: - Correction: ABSTRACT Details: Wrong : This study was undertaken to investigate the following two problems: (a) Whether metacontrast masking functions can be consistently classified into U-shaped functions and monotonic functions on the basis of the energy ratio of test stimulus (TS) to mask stimulus (MS), and (b) which type of metacontrast masking function arises in what part of the visual pathway. Subjects were instructed to make magnitude estimations in regard to brightness and size (or clearness of shape) of the TS.
In Experiment I, the masking functions were obtained by varying either MS luminance (variable luminance condition) or MS duration (variable duration condition) under monoptic and dichoptic observations. Both conditions adopted MSs having identical amount of energy (Table 1). Under the variable luminance condition, the U-shaped functions were found in both observations. Especially in the monoptic observation, estimated sizes generally decreased as the luminance of the MS increased throughout the range of SOAs from 0 to 55ms where the masking functions reached their lowest points (Fig. 3). Under the variable duration condition, on the other hand, curves of the masking functions showed a gradual shift from U-shaped to monotonic patterns as the MS duration increased in both observation conditions (Fig. 4). Estimated brightness of the TS had a tendency similar to the above mentioned one found in estimated size in the function shape.
In Experiment II, it was examined whether the monotonic function could be obtained or not when the MS luminance was increased much more than in Experiment I. In the high MS luminance (1874.0cd/m²), the monoptic observation produced the monotonic function, while the dichoptic observation resulted in the U-shaped one even under the high MS luminance (Fig. 5).
These results seemed to suggest that the types of the masking function were determined by the duration of the MS and by the ratio of the TS duration to the MS, instead of the energy ratio of the MS to the TS as demonstrated by the previous investigations.
Experiment III was conducted to test the above hypothesis observing the masking function when the MS duration was increased with the MS and the TS energies being kept equal. The hypothesis predicted that the monotonic function should be obtained when the MS duration is much longer than the TS duration, even if both energies are equal. The above hypothesis was confirmed by the fact that the obtained curves changed from the U-shaped function to the approximately monotonic one as the MS duration increased (Fig. 6).
The following points are discussed. (a) The most powerful factors determining the types of the metacontrast masking function seems to be the duration of the MS and the relation between the TS and the MS duration. (b) The monotonic function under the high MS luminance might be produced when the metacontrast at the short SOAs is combined with the masking which occurs in a peripheral level. (c) The failure in verifying the U-shaped functions which has been reported in the previous investigations seems to be due to the use of the relatively long MS duration.
Right : To investigate the factors determining the types of metacontrast masking function, masking functions were examined by varying either luminance or duration of mask stimulus (MS) under monoptic and dichoptic observations. Under dichoptic-variable luminance condition, U-shaped functions were obtained regardless of the MS luminance, but monotonic ones were found under monoptic with very high luminance. Under both observations with the variable duration condition, function changed from U-shaped to monotonic as the MS duration increased. Furthermore, when the test stimulus (TS) energy was equal to that of the MS, a long MS duration yielded a function close to monotonic one. It was suggested that types of metacontrast function might be determined by the MS duration and the duration ratio of TS to MS, not by the energy ratio.

Abstract

To investigate the factors determining the types of metacontrast masking function, masking functions were examined by varying either luminance or duration of mask stimulus (MS) under monoptic and dichoptic observations. Under dichoptic-variable luminance condition, U-shaped functions were obtained regardless of the MS luminance, but monotonic ones were found under monoptic with very high luminance. Under both observations with the variable duration condition, function changed from U-shaped to monotonic as the MS duration increased. Furthermore, when the test stimulus (TS) energy was equal to that of the MS, a long MS duration yielded a function close to monotonic one. It was suggested that types of metacontrast function might be determined by the MS duration and the duration ratio of TS to MS, not by the energy ratio.

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