Baddeley (1966b)

AIM: To examine the coding of the LTM store.

METHOD: Baddeley conducted a series of three experiments. While all three experiments focused on the coding of LTM, this summary will focus on experiment three, which negated the effects of STM. Baddeley used an independent groups design, where each participant took part in one of four conditions. Each conditioned consisted of four trials: List A consisted of 10 acoustically similar words (15 participants); List B consisted of 10 acoustically dissimilar words (20 participants); List C consists of 10 semantically similar words (16 participants); List D consisted of 10 semantically different words (21 participants). Following each presentation of the word list, the participants completed a STM task to prevent rehearsal. Thereafter, they were allowed 1 minute to write out the 10-word sequence. Following the four trials, the participants completed a 15-minute task, which was a self-paced digit copying task. They then attempted to recall the word sequences again (re-test), to examine the effect on LTM.

RESULTS: There was no significant difference between the acoustically similar/dissimilar words. However, there was a significant difference found between the semantically similar/dissimilar words. Baddeley found that the participants were significantly worse at recalling the semantically similar words (see Graph 1).

CONCLUSION: The results clearly suggest that the LTM store codes semantically. Words which are semantically similar, when learned over a series of four trials, are poorly recalled in comparison to words which are semantically different. When the participants attempted to recall information from their LTM store, the semantically similar words become confused, making the task more difficult. This explains why the performance was significantly worse in the semantically similar condition, in comparison to the semantically different condition.