Linguistics Encyclopedia.pdf

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tasks to be performed with the stimuli as well as their status in the listener’s linguistic
system.
Clearly, the relationship between the acoustic/ phonetic properties of speech and its
processing in the brain is complex. In attempting to understand this relationship, it is also
important to make a distinction between the auditory properties of speech, which are pre-
or alinguistic, and the phonetic properties of speech, which are linguistic (Pisoni, 1973).
The difference is not always readily apparent, and the task is further complicated by the
fact that what may be perceived as auditory in one language may be perceived as
phonetic in another. It is well known that languages often utilize different perceptually
salient cues, and these differences have measurable behavioural consequences
(Caramazza et al., 1973; Mack, 1982, 1984; Flege and Hillenbrand, 1986).
SELECTED ISSUES IN AUDITORY PHONETICS
One recurrent theme in auditory phonetics revolves around the question ‘Is speech
special?’ In other words, is speech perception essentially akin to the perception of other
acoustically complex stimuli or is it somehow unique? Several main sources of evidence
are often invoked in discussions of this issue.
First, it is apparent that the frequencies used in producing speech are among those to
which the human auditory system is most sensitive, and certain spectral and temporal
features of speech stimuli correspond to those to which the mammalian auditory system
is highly sensitive (Kiang, 1980; Stevens, 1981). This suggests that there is a close
relationship between the sounds which humans are capable of producing and those which
the auditory system most accurately perceives.
Moreover, experiments with prelinguistic infants have demonstrated that linguistic
experience is not a necessary precondition for perception of some of the properties of
speech, such as those involved in place and manner of articulation (Eimas et al., 1971;
Kuhl, 1979).
Other evidence is based upon what has been termed categorical perception. It has
repeatedly been shown that a continuum of certain types of speech stimuli differing with
respect to only one or two features is not perceived in a continuous manner. Categorical
perception can be summarized in the simple phrase: ‘Subjects can discriminate no better
than they can label.’ That is, if subjects are presented with a continuum in which all
stimuli differ in some specific and equivalent way, and if those subjects are required to
label each stimulus heard, they will divide the continuum into only those two or three
categories, such as /d–t/ or /b–d–g/, over which the continuum ranges. If these subjects
are also presented with pairs of stimuli from the same continuum in a discrimination task,
they do not report that members of all acoustically dissimilar pairs are different, even
though they actually are. Rather, subjects report as different only those pair members
which fall, in the continuum, in that region in which their responses switch from one
label to another in the labelling task. It has been argued that non-speech stimuli, such as
colours and tones, are not perceived categorically; hence the special status of categorical
perception of speech. It is important to note, however, that not all speech stimuli are
perceived categorically. For example, steady-state vowels—vowels in which there are no
abrupt changes in frequency at onset or offset—are not (Fry et al., 1962).