Word frequency effects on free recall and recognition in patients with schizophrenia.

Background: Word frequency paradigms have been used repeatedly in healthy populations to help understand the functioning of verbal memory. We investigated the word frequency effects in a sample of patients with schizophrenia, assuming these data may shed light on certain encoding processes.

Methods: Two mixed lists of high- and low-frequency words were presented to 46 patients with schizophrenia and 43 healthy control subjects. List learning was followed by free recall and recognition in immediate and delayed conditions.

Results: Overall the high-frequency words were better recalled, whereas the low-frequency words were better recognised. The lack of interaction with diagnosis indicates that these effects were equivalent in both groups. In immediate recognition, the discrimination deficit for the high-frequency words in patients tended to be increased relative to that for the low-frequency words, suggesting greater impairment in the encoding of those words.

Conclusion: It is argued that the encoding of the distinct low-frequency words is less efficient in patients, but qualitatively unimpaired. By contrast, the familiar words might be more difficult for patients to encode, as they are more easily confused with other common words stored in long-term memory.