The representation of arithmetic facts in memory: results from retraining a brain-damaged patient.

This single case study was designed to gather evidence regarding whether the mental representations mediating multiplication fact retrieval make use of single or multiple codes. MC is a brain-damaged volunteer whose numerical processing impairments were limited to multiplication fact retrieval. He relearned three sets of multiplication facts. Each set was relearned in one of three input formats: Arabic, written verbal, or spoken verbal. Following training all facts were tested in all input formats. MC's posttraining performance was virtually error free and showed no effects of input format. However, reaction-time data showed fact retrieval was fastest when the training format matched the test format. Results are discussed in relation to single- and multiple-code models of multiplication fact retrieval.

Inhibition, contextual segregation, and subject strategies in list method directed forgetting.

This experiment tested alternative explanations of list method directed forgetting effects. Two word lists were studied by 135 subjects. Between lists, subjects were instructed to remember both lists (remember group), remember both lists as well as in which list words were studied (segregate group), or to forget the first list and remember the second (forget group). All subjects took both recall and recognition tests with test order varied between subjects. Among subjects who took the recall test first, the forget group showed a directed forgetting effect (poorer performance on List 1 than List 2) with both recall accuracy, recall typing time, and recognition reaction time measures. Contextual segregation of List 1 words by forget subjects was ruled out as a sufficient cause of the effect. Limited support was obtained for a differential rehearsal explanation of the effect. Within-group comparisons and findings of release from directed forgetting support inhibitory processes as the major cause of the directed forgetting effect.

Picture memory: recognizing added and deleted details.

When people are presented simple and complex pictures and then tested in a same-changed recognition test with a simple or complex form of each, d' is greater for the simple than the complex picture (Pezdek & Chen, 1982). The results of three experiments confirm the robustness of this "asymmetric confusability effect" and test a model of the processes underlying this effect. According to the model, pictures are schematically encoded such that the memory representation of both simple and complex pictures is similar to the simple form of each. In Experiment 1, a sentence was presented that described the central schema in the picture prior to subjects' viewing each picture. This manipulation exaggerated the asymmetric confusability effect; schematic processing thus underlies the effect. Results of Experiment 2 refute the hypothesis that the effect results from subjects erroneously anticipating a recall test rather than a recognition test. Furthermore, although some of the nonschematic elaborative information in complex pictures is stored in memory, it is difficult to retrieve to verify that something is missing when complex presentation pictures are changed to simple test pictures (Experiment 3). Thus, although people are able to distinguish large sets of old pictures from new distractor pictures, their ability to detect missing elaborative visual details is more limited.