Effects of frequency on the auditory perception of open- versus closed-class words

Over the past couple of decades, it has been repeatedly investigated whether open-class items are processed in a different way from closed-class items. Most studies, however, have been bedeviled by difficulties in controlling all relevant distinctions between open- and closed-class items. For example, whereas open-class items have a relatively low frequency of occurrence, closed-class words have a very high frequency. The current study investigates auditory lexical decisions on open- versus closed-class items when the effect of frequency is controlled. Results revealed faster responses to high frequency open-class items when compared to closed-class items of similar frequency. Furthermore, responses to both low frequency open-class items and nonwords were significantly different from the responses to the high frequency open-class items, but not from responses to the high frequency closed-class items. Similar latencies for closed-class items and nonwords suggest that the open/closed-class distinction might be due to the clear lexical meaning of open-class items as opposed to the more grammatical function of closed-class words