Perceptual magnet effect in the light of behavioral and psychophysiological data.

Finnish speaking adults categorized synthetic vowels, varying in the frequency of the second formant (F2), as either /y/ or /i/. Two subject groups emerged: "good" and "poor" categorizers. In a /i/ rating experiment, only the good categorizers could consistently label their best /i/ (the prototype, P), being low in the F2 continuum. Poor categorizers rated /i/'s with high F2 values as Ps. In a same/different (AX) discrimination experiment, using the individual Ps and nonprototypes (NPs), it was more difficult for good categorizers to detect small F2 deviations from the P than from an NP (the "perceptual magnet effect"). For poor categorizers, the opposite effect was found. The same stimuli were used to record the mismatch negativity (MMN), an ERP component reflecting preattentive detection of deviations from a standard sound. For the good categorizers the MMNs were lower for Ps than for NPs; for the poor categorizers the MMNs for Ps and NPs did not differ significantly. The results show that individual listeners behaved differently in categorization and goodness rating but in the same way in attentive (AX) discrimination, being the poorest at about the same F2 location. The perceptual magnet effect was indicated in the good categorizers both by behavioral and psychophysiological (MMN) discrimination data.