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. Author manuscript; available in PMC: 2015 Jul 1.
Published in final edited form as: Psychol Sci. 2014 May 8;25(7):1325–1336. doi: 10.1177/0956797614529978

Figure 1.

Figure 1

Hypothesis and Experimental Design (A) An acoustical effects processor was used to alter the first formant frequency (F1) of the vowel sound in “head” so that it sounded more like “had” (black arrows). It was hypothesized that individuals compensate for this alteration by lowering produced F1 (grey arrows) until their heard production once again falls within the perceptual range of “head”. Changing the point of perceptual distinction between “head” and “had” should thus alter the amount of compensation (blue versus red bars). (B) Two groups of 21 female subjects were tested. Unaltered production of “head” and “had” (baseline) was followed by three perceptual tests designed to measure (PT1) and then alter (PTr2 and PTr3) the perceptual boundary between “head” and “had”. Perceptual training was followed by production of the word “head” with an increase in F1 so that the word sounded more like “had”, a final measurement of the perceptual boundary (PT4), and unaltered productions of “head” and “had” to “washout” learning.