 Uniqueness point

A word's uniqueness point is the earliest point in its spoken form at which the sounds heard so far distinguish it from all competing words in a specified vocabulary. It connects a cohort model of spoken word recognition to the changing size of the lexical cohort.^[ref]

For an invented vocabulary, let three word forms be the phoneme sequences $pata$, $pana$ and $pita$, with spaces ignored and each symbol representing one phoneme. The third word becomes unique after $pi$, while the first two remain ambiguous after $pa$ and diverge at the following consonant. Uniqueness can therefore precede the end of a word.

This is a property of the chosen vocabulary and transcription, not a universal timestamp attached to a spelling. Adding another word beginning $pi$ changes the example. A word that is a complete prefix of another may require an end-of-word cue. Measured reaction time also includes perceptual, decision and motor processes, so it need not equal the lexical uniqueness time.