MASKING

Intervention which makes a written or spoken word less easy to perceive. Masking is used experimentally to determine which cues in the signal are used by the reader or listener and what level of masking prevents recognition.

Visual masking. Evidence from visual masking supports the view that readers process a word at many different levels– feature, letter and whole word. Briefly shown a word on a screen, subjects find it more difficult to report what the word is if it is immediately followed by another stimulus.

In brightness masking, the subject is presented with a bright screen immediately after the word. If the brightness mask follows the word very rapidly, it interferes with recognition to such a degree that the word becomes indistinguishable from its background. Subjects report seeing a word for a reasonable length of time, but claim that it was not sharply enough defined. Brightness masking is said to block processing by interfering with the detection of features (the shapes that make up each letter).

In pattern masking, the target word is followed immediately by a stimulus that conflicts with it. The stimulus might be a feature mask, a random assortment of lines and curves like those in actual letters. The newly introduced features interfere with those just detected in the target word and with the process of assembling them into letters. The result, again, is a reduced ability to identify the word. This time, subjects report seeing a sharply defined word, but not for long enough to recognise it. In another type of pattern mask, the interfering stimulus is an actual word. These word masks appear to interfere with processing at both letter and word level.

Auditory masking. Experimenters use auditory masking to measure the amount by which the audibility of one sound is reduced by the presence of another (the ‘masker’). With simultaneous masking, the audibility of a signal is most strongly affected when the added sound has frequency components which are similar to the target one. This is taken as evidence of how selective the ear is in distinguishing frequencies. The decibel level of the masker is also an important factor: the effect on audibility relates closely to the ratio between signal and masker. Simultaneous masking thus has practical applications: showing, for example, what level of machinery noise prevents spoken communication between workers in a factory.

Audibility can also be affected by forward masking, where added sounds immediately precede the stimulus, and backward masking, where they follow it. The degree of forward masking is determined by the duration of the masker and how closely it precedes the target; here, increases in decibel level do not have a proportionate effect on audibility. Forward masking may possibly be caused by a reduction in the sensitivity of the ear following the masker or by the hearer retaining the masker signal after it has finished.

See also: Intelligibility, Noise, Reading: decoding

Further reading: Harris and Coltheart (1986: 153–9)

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مواضيع ذات صلة

MEANING CONSTRUCTION

MEAN LENGTH OF UTTERANCE (MLU)

McGURK EFFECT

MARKEDNESS

MAPPING (FORM-MEANING)

LOWER-LEVEL PROCESSING

LONG-TERM MEMORY (LTM)

LOGOGEN

LISTENING: HIGHER-LEVEL PROCESSES

LINGUISTIC RELATIVITY

LEXICAL STRESS

LEXICAL STORAGE