Word frequency effects for a closed-set word identification task.

Previous work demonstrated that adults achieved higher performance scores than young children on a 4-alternative forced-choice (4 AFC), picture-pointing speech identification task even though all stimuli (words and pictures) had been developed to be familiar to 3-year-old inner-city children. It was hypothesized that these results reflected 'word frequency effects' in the sense that, even though children knew the words, adults had much greater experience with the stimuli and, consequently, required less acoustic information for correct performance. In the current study, this hypothesis of word frequency effects was tested by creating new materials in which the stimulus items (recorded words and pictures) remained the same but new picture foils representing less frequently occurring words replaced the incorrect response alternatives. According to Broadbent's word frequency, response bias views, it was hypothesized that adults would show improved performance on the modified test materials, compared to the original ones. Data supported this hypothesis and also showed that, in children, the magnitude of word frequency effects is related to receptive vocabulary skills. This phenomenon needs to be considered in developing clinical tests of speech or language that have a closed-set format.