|Slater I 193
Phonetics/Eimas: In their study (Eimas et al. 1971(1)) (>Language development/Eimas, >Language development/psychological theories) Eimas et al. presented both within-category and
between-category differences to infants, and the expectation was that only the between-category differences would be discriminated.
For historical accuracy, it is important to note that Moffitt (1971)(2) conducted a study of speech discrimination in 5—6 month olds that appeared in print before Eimas et al. (1971)(1), but only a between-category /ba/ — /ga/ contrast was tested. Using a heart-rate measure, Moffitt showed that infants can discriminate this contrast before six months of age.
Slater I 192
Categorical Perception (CP): This special mode of perception was characterized by two crucial properties:
(a) tokens presented from a physical continuum were identified (labeled) as a member of one category or the other, with a sharp transition in identification (ID) at the category boundary, and
(b) failure of within-category discrimination and a peak in between-category discrimination for tokens that straddled the category boundary.
Method of the study: High Amplitude Sucking (HAS) - was a form of operant conditioning in which sucking behavior led to the presentation of a reward.
Slater I 194
Eimas et al. (1971)(1) used the HAS technique to measure the discrimination of two tokens that adults identify as different (20 msec VOT (voice onset time) = /ba/ and 40 msec VOT = / pa/), two tokens that adults identify as the same (-20 msec and O msec VOT = /ba/; 60 and 80 msec VOT = /pa/), and as a control condition two tokens that were identical (one of the six values of VOT: -20,0,20,40,60,80 msec). The minus VOT value denotes a sound for which the vocal chords begin to vibrate slightly before the sound is released.
Thus, there was a between-category condition, a within-category condition, and a no-change control condition.
Results: Only infants in the between-category condition showed evidence of discrimination; that is, they showed a significant recovery of sucking rate after the change in the speech stimulus. Infants in the within-category condition showed no evidence of an increase in sucking rate to a change in the speech stimulus, even though the physical change was of the same magnitude (20 msec) as in the between-category condition. And infants in the control condition did not show spontaneous recovery of sucking to the same repeating speech stimulus, thereby ruling out false evidence of discrimination in the between-category condition.
Eimas et al.: “The discontinuity in discrimination at the region of the adult phonemic boundary was taken as evidence for categorical perception.” (1971(1), p. 306).
“The means by which the categorical perception of speech, that is, perception in a linguistic mode, is accomplished may well be part of the biological makeup of the organism and, moreover, that these means must be operative at an unexpectedly early age.” (p. 306). >Language development/Eimas.
1. Eimas, P. D., Siqueland, E. R.,Jusczyk, P., & Vigorito, J. (1971). Speech perception in infants. Science, 171, 303-306.
2. Moffitt, A. R. (1971). Consonant cue perception by twenty- to twenty-four-week-old infants. Child
Development, 42, 717—731.
Richard N. Aslin, “Language Development. Revisiting Eimas et al.‘s /ba/ and /pa/ Study”, in: Alan M. Slater and Paul C. Quinn (eds.) 2012. Developmental Psychology. Revisiting the Classic Studies. London: Sage Publications_____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. The note [Author1]Vs[Author2] or [Author]Vs[term] is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition.
|Eimas, Peter D.
Alan M. Slater
Paul C. Quinn
Developmental Psychology. Revisiting the Classic Studies London 2012