A phonological input buffer for numbers

The ability to comprehend oral numbers is central to numerical literacy, yet the mechanisms enabling it are still poorly understood. Here we show that, as some have hypothesized, short-term memory is involved in this process, and we also show how. We report two adults with developmental short-term memory deficit. They performed poorly in writing numbers to dictation and in other tasks requiring number comprehension, but not in tasks requiring other aspects of number processing. Their performance level was modulated by the memory load imposed by the task, and they made a variety of error types – digit substitutions as well as violations of the number’s syntactic structure. We conclude that their deficit was in a short-term memory store which serves the verbal-phonological input of numbers – a phonological input buffer for numbers. Detailed error analysis suggests that this buffer serves as a workbench in which number words are stored before parsing their syntactic structure. Based on these and previous findings, we propose a detailed cognitive model for the verbal-phonological input of numbers, in which the phonological input buffer has a central role.