Three Areas of Experimental Phonetics
Peter Ladefoged, 1967

Stress and Respiratory Activity
Area 1

The Nature of Vowel Quality
Area 2

Units in the Perception and Production of Speech
Ladefoged's click perception experiments show that listeners cannot accurately describe the temporal position of a click or an "s" sound superimposed on speech. On the average, listeners heard the added sounds 1 to 2 words earlier than they actually occurred.

Ladefoged interprets this result as saying that the "phoneme" is not a psychologically or physiologically useful unit for speech perception.

In a second set of experiments, subjects attempted to pronounce various words with earphones playing a noise loud enough that the subjects could not hear themselves and also with and without having taken a lozenge which completely numbed the inside of the mouth and lips, preventing the subject from perceiving any tactile feedback during pronunciation.

The loss of tactile feedback causes more severe changes in pronunciations than the loss of auditory feedback.

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