A matrix is presented of the errors of perception made by 135 men and women listening to three male and three female speakers reading aloud different randomized lists constructed from the letters of the alphabet and the digits 1–9, heard in white noise. Data from a short-term memory (STM) experiment, using simultaneous visual presentation and immediate ordered recall of two selected vocabularies of nine letters and the digits 1–9, are cited as evidence of phonemic confusion between letters and digits in STM.