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Results for “Perceptual Masking”

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At least 127 records · Page 7Linked to original sources
PubMed2001

The attenuation of perceived image smear during saccades.

The perception of image smear for a target flashed during a saccade is attenuated if the target remains visible after the eye movement ends, a result that has been attributed to backward masking. In this experiment, normal observers matched the length of perceived smear in two conditions that were designed to produce comparable retinal stimulation and, therefore, similar amounts of masking. In the saccade condition, a small stationary bright dot was illuminated for 5-640 ms, starting near the onset of a horizontal saccade. In the fixation condition, the bright dot moved right or left at 50, 100, or 200 degrees s-1 while the observer viewed a stationary target and, thereafter, remained stationary. As expected, in the saccade condition perceived smear first increased and then decreased as the duration of the flashed dot extended beyond the duration of the eye movement. However, perceived smear was substantially greater in the fixation condition for stimulus durations that were longer than the period of dot motion. Under the conditions of our experiment, the attenuation of perceived image smear during saccades is attributable primarily to the operation of an extraretinal eye movement signal, rather than to backward masking.

Fixation, Ocular↗
PubMed1986

Vibrotactile frequency recognition: forward and backward masking effects.

Forward and backward vibrotactile recognition masking was investigated in 4 subjects with 240-Hz and 160-Hz targets of 20 ms duration and four 200-Hz masks, using interstimulus intervals (ISIs) ranging from -500 to 500 ms. Two of the masks (short) were 20 ms and two (long) were 200 ms in duration. One of each set of masks was matched in subjective intensity to the targets, but the others were more intense. The range of ISIs over which masking was obtained was comparable to that found by Massaro (1970) with auditory stimuli. Both short masks produced more masking than either long mask except at short ISIs. Larger mask intensities increased masking only at very short ISIs, and longer mask durations increased backward but not forward masking.

Discrimination Learning↗
PubMed2002

Antimasking aspects of harp seal (Pagophilus groenlandicus) underwater vocalizations.

Underwater sounds are very important in social communication of harp seals (Pagophilus groenlandicus) because they are the main means of long- and short-distance communication. Individual harp seals must try to avoid being masked and emit only those calls that will benefit them. Underwater vocalizations of harp seals were recorded during the breeding season. The physical characteristics associated with antimasking attributes of 16 call types were examined. Rising frequency or increasing amplitude within calls were not common. Most of the calls ended abruptly (range 145-966 dB/s), but call onset was more gradual. At high calling rates (95.1-135 calls/min) there were significantly more calls overlapping temporally than at medium (75.1-95 calls/min) or low (35-75 calls/min) calling rates, but even at the highest calling rates, 79.1% of the calls were not overlapped. When 2, 3, or 4 calls overlapped, there were significantly fewer frequency separations of less than 1/3 octave than would be expected by chance. This is important because sounds that are separated by less than 1/3 octave likely mask each other. When 2-4 calls are occurring simultaneously, only 4.5% to 14.2% are masked by virtue of being within 1/3 octave from their nearest neighbor. None of the overlappping calls was of the same type. This suggests that the seals are actively listening to each other's calls and are not randomly using the different call types. Harp seals use frequency and temporal separation in conjunction with a wide vocal repertoire to avoid masking each other.

Animal Communication↗
PubMed1987

Speech masking. I. Simultaneous and nonsimultaneous masking within stop /d/ and flap closures.

This article reports on investigations of the relative roles of simultaneous and nonsimultaneous masking on detection thresholds using natural speech utterances. Thresholds were obtained for 15-ms probe tones placed in the stop or flap closures of /ada/ and /idi/. Threshold elevations due to simultaneous and nonsimultaneous masking could be explained by the dynamics of neighboring speech spectra. Nonsimultaneous effects were related to spectra at least 30 ms around the probe tone. Although simultaneous masking is usually stronger than nonsimultaneous masking, the relative amplitude of adjacent speech segments in natural speech is sufficiently high near formant regions to cause noticeable effects of nonsimultaneous masking.

Adult↗
PubMed2000

Channel selection with non-white-noise masks.

It is frequently assumed that the accuracy with which luminance gratings can be detected depends solely on the signal-to-noise ratio at the output of a single linear channel. Proportionality between threshold elevation and power spectral density is implicit in this assumption. I demonstrate that this proportionality does not hold for 1-cycle/degree gratings masked by low-pass noise with a 0.5-cycle/degree cutoff frequency. This implies that different channels can mediate detection, depending on the contrast of masking stimuli.

Humans↗
PubMed2002

Gestalt grouping and common onset masking.

A four-dot mask that surrounds and is presented simultaneously with a briefly presented target will reduce a person's ability to identity that target if the mask persists beyond target offset and attention is divided (Enns & Di Lollo, 1997, 2000). This masking effect, referred to as common onset masking, reflects reentrant processing in the visual system and can best be explained with a theory of object substitution (Di Lollo, Enns, & Rensink, 2000). In the present experiments, we investigated whether Gestalt grouping variables would influence the strength of common onset masking. The results indicated that (1) masking was impervious to grouping by form, similarity of color, position, luminance polarity, and common region and (2) masking increased with the number of elements in the masking display.

Humans↗
PubMed2001

The roles of attention and awareness in the false recognition effect.

Jacoby and Whitehouse (1989) reported that masked words can unconsciously bias memory judgments. Others suggest that these results cannot be taken as evidence that words are perceived without awareness, as Jacoby and Whitehouse claimed. In the present experiments, participants' ability to attend to briefly presented context words was manipulated by masking the context words and by an instructional manipulation. In Experiment 1, masked context words increased false recognitions. Different from Jacoby and Whitehouse's results, nonmasked context words showed a similar pattern. In Experiment 2, these effects were replicated and an attended condition was added in which participants read the context words aloud and tried to remember them. False recognition was increased in both masked and unmasked conditions and decreased in the attended condition. These results suggest that the condition for increase or decrease in false recognition is not whether a stimulus is seen or not but whether a stimulus is attended. They suggest that the qualitative difference criterion proposed by Jacoby and Whitehouse is insufficient for determining whether participants are aware of masked presentations.

Adult↗