Analyse a ‘free-recall’ experiment as an evidence for a two process theory

An analysis of ‘free-recall can also provide us evidence for a two-process theory. The free-recall task is War to the one you face when asked to name all the people present at the last large party you (ended. In the typical free-recall experiment, a list of unrelated words is presented to the subject one la time.

Later the subject attempts to recall as many words as possible in any order. The result of principal interest is the probability of recalling each item in a list as a function of its place in the list or Serial presentation position.”

The increased probability of recall for the first few words in the list is called the regency effect. According to a two-process theory the regency effect is due to retrieval from STM, and the earlier portions of the serial position curve reflect retrieval from LTM only. In one experimental procedure the subject is required to carry out a difficult arithmetic task for 30 seconds immediately following presentation of the list, and is then asked to recall. One can assume that the arithmetic task causes the loss of all the words in STM, so that recall reflects retrieval from LTM only.

The regency effect is eliminated when this experiment is performed; the earlier portions of the serial position curve are unaffected

If variables that influence LTM but not STM are manipulated, the regency portion is relatively unaffected, but the earlier portions of the curve change. For example, one such variable is the number of words in the presented list. A word in a longer list is less likely to be recalled, but the regency effect is unaffected by list length

Increases in the rate of presentation during study decrease the likelihood of recalling words preceding the regency region but leave the regency effect largely unchanged

The probability of recalling words as a function of their serial position within each list can be plotted for end-of-session recall and compared with the serial position curve for recall immediately following presentation (Figure). As predicted, the primacy effect remains in the delayed recall curve, but the regency effect is eliminated. To summarize, the regency region of the serial position curve appears to reflected retrieval from both STM and LTM, whereas the curve preceding the regency region reflects from LTM only.