"Penguins don't fly": An investigation into the effect of typicality on picture naming in people with aphasia.

BACKGROUND: PREVIOUS RESEARCH HAS HIGHLIGHTED PSYCHOLINGUISTIC VARIABLES INFLUENCING NAMING ABILITY FOR INDIVIDUALS WITH APHASIA, INCLUDING: familiarity, frequency, age of acquisition, imageability, operativity, and length (Nickels & Howard, 1995) and a potential link between typicality and generalisation to untreated items in intervention (Kiran, Sandberg, & Sebastian, 2011). However, the effect of concept typicality (the extent to which an item can be considered a prototype of a category) on naming in aphasia warrants further examination.

AIMS: To investigate first whether typicality can be reliably rated across a range of natural semantic categories and second whether, and if so in which direction, typicality influences naming performance for people with aphasia. To provide quantitative and qualitative information on typicality for a set of stimuli for use in future research.

METHODS & PROCEDURES: Typicality ratings were obtained and the results compared with those in the existing literature. The influence of typicality on picture naming was investigated employing both matched sets (high and low typicality matched for other psycholinguistic variables) and logistic regression analyses for the group and individual participants with aphasia ( n = 20).

OUTCOMES & RESULTS: Typicality rating correlated strongly with ratings obtained in previous research (Rosch, 1975: r = .798, N = 35, p < .001; Uyeda & Mandler, 1980: r = .844, N = 47, p < .001). Typicality was a significant predictor of picture naming for the group and some individuals, with generally better performance for typical items. This was demonstrated in both matched sets and regression analyses. However, other psycholinguistic variables proved more strongly related to naming success, particularly age of acquisition.

CONCLUSIONS: Typicality can be rated reliably and should be considered alongside other psycholinguistic variables when investigating word retrieval and intervention in aphasia. Further research is necessary to accurately model the direction of typicality effects found in word retrieval. Finally, the differing nature, size, and internal structure of categories require further exploration when investigating typicality effects.