Immediate free recall of drug names: effects of similarity and availability.

The prescribing frequency, subjective familiarity, and two measures of similarity as predictors of error in immediate free recall of drug names were assessed. The study design utilized prospective, computer-based, word memory experiments in which 30 pharmacists and 66 college students were asked to immediately recall 15 lists of three three-syllable drug names. Intralist similarity was systematically varied. The number of words forgotten or incorrectly recalled was then examined as a function of similarity, subjective familiarity, and prescribing frequency. The primary outcome measure was the number of item errors in free recall. Pharmacists made fewer errors than college students. Familiarity reliably enhanced item recall among both pharmacists and college students. Prescribing frequency enhanced recall among both pharmacists and college students except when college students recalled generic names. Orthographic (i.e., spelling) similarity was reliably associated with item recall in both groups. Fewer errors were made when lists were more orthographically similar. Among pharmacists, there was an inverted U-shaped relationship between phonologic (i.e., sound) similarity and item errors, with the fewest errors being made on the most similar lists. Among college students, phonologic similarity was not reliably associated with item errors. Frequently prescribed and subjectively familiar drug names are more accurately recalled than rarely prescribed and unfamiliar names. Orthographically similar lists of drug names are easier to recall than dissimilar lists because similarity provides cues that facilitate the retrieval of degraded short-term memories. The effects of similarity, familiarity, and frequency on short-term memory of drug names vary as a function of task and stimulus characteristics.