A comparison of metamemory judgements and forgetting rates for item and associative recognition for normal and closed-head injured populations

Metamemory, in particular memory monitoring during a memory task, was investigated in a closed—head injured (CHI) population and a normal (control) population. Prediction ratings were used to determine memory monitoring at time of encoding, and postdiction ratings were used to determine memory monitoring at time of retrieval. Item and associative information for concrete and abstract words were tested using a forced—choice recognition test procedure. Forgetting rates for these two types of information (item and associative) were examined by analyzing immediate and final recognition memory performance. Results indicated that the CHI group had a lower overall level of recognition performance, however the pattern of performance was similar for both groups. Both the control and CHI group demonstrated the concreteness effect, but this effect was found to be dependent on the type of recognition test and time of test. In particular, the concreteness effect was only observed for associative recognition on the final test. Furthermore, there was a steep decline over time for associative recognition of abstract material; such a consistent pattern of decline has not previously been reported for associative recognition. There was no significant relationship between memory monitoring at time of encoding (prediction) and memory performance for either group, however for the control group (but not the CHI group) there was a significant relationship between memory monitoring at time of retrieval (postdiction) and memory performance. These findings suggest that, for the CHI group, recognition performance for item and associative information is quantitatively but not qualitatively different from that of the control group. Furthermore, findings suggest that there may be a partially preserved ability in the CHI group to exhibit the concreteness effect, depending on the experimental conditions. The significance of these findings are discussed in relation to existing theory and possible implications