False recognition following frontal lobe damage: The role of encoding factors

This paper reports a series of experiments on patient JB, a man with memory difficulties following damage to the left frontal lobe. The primary charac teristic of JB's recognition memory impairment is a high level of false rec ognition together with a normal hit rate. The hypothesis that JB's false re cognition reflects an over-reliance on familiarity is considered, but disco unted on the basis that the false alarm rate is not affected by increasing the similarity between distracters and targets, and remains high when nonwo rd stimuli are used. It is suggested, instead, that JB relies on a poorly f ocused memory description, which lacks item-specific detail but contains mo re general, low-level properties of the target items-these properties being held by many distracter items as well. This deficit is considered to arise because of damage to frontally mediated control processes involved in the selection of elements for memory encoding. An encoding deficit is supported by the fact that JB's false recognition is significantly reduced by orient ing instructions, and is eliminated when his remote memory is subjected to recognition testing. In contrast, it is shown that manipulations at the lev el of retrieval (e.g. restricting the number of "old" responses) have littl e effect on his false recognition.