The phoneme "ba" differs from the phoneme "pa" primarily in the voice onset time, namely the delay between the opening of the lips to produce the consonant and the vibration of the vocal chords required to produce the vowel. By varying systematically the voice onset time and asking observers to report which phoneme is heard, "ba" or "pa", one finds that phoneme perception is ___________, in that (a) one hears either "ba" or "pa", even with intermediate voice onset times, and (b) the phonemic boundary, measured as a function of voice onset time, is quite __________.
nonlinear - sharp
invariant - sharp
categorical - sharp
consonantal - diffuse
linear - shallow