The acoustic correlates of "speechlike" : a use of the suffix effect

Used the suffix effect to investigate the conditions under which a sound is treated by the acoustic system as speechlike and reaffirmed the essentially precategorical nature of the memory source. Ss participating in the experiments were 21-65 yr old females. Exps I-XIII showed that a completely regular sound (in which a single pitch pulse from a naturally spoken vowel was repeatedly reproduced) still produced a substantial suffix effect. In addition, a natural sound had to be quite severely filtered before the suffix effect began to vanish. However, a combination of regularity and filtering neutralized the effect of the sound as a suffix. Exp XIV and XV showed that the classification parameters could be shifted by changing the acoustic properties of the stimulus list. When Ss rated a variety of sounds for their naturalness and their similarity to the original suffix (Exps XVII-XXII), these measures were sensitive to the filtering operations but not to regularity. These results reinforce the view of a distinction between central, subjectively controllable factors and a strong precategorical effect.