Retention in short-term memory was studied by manipulating rates of presentation (1-10 digits/sec), the type of digit presentation (spoken, computer spoken, and visually presented), the type of item (single digits, paired digits, and nonsense sounds), and the type of test (recall and recognition). Performance in short-term memory experiments is attributed to interactions among 3 different processes: acquisition, retention, and decision. Rate of presentation, length of list, type of item, and modality seemed mainly to affect the initial acquisition of items in memory. The rate of forgetting depended mainly upon the number of items presented between the critical item and its test. (PsycINFO Database Record (c) 2006 APA, all rights reserved)