Learning Objectives

The previous two chapters focused on the brain mechanisms underlying successful long-term memory. The flip side of memory success is memory failure, and these processes are intimately linked. As will be discussed in more detail within this chapter, understanding memory failure furthers our understanding of memory success. Memory failure can be broadly classified into forgetting and memory distortion. Everyone is experienced with forgetting and, even though we are almost never aware of it, memory distortion. This chapter begins by reviewing the brain regions associated with typical forgetting, which can be attributed to a lack of attention during encoding (section 5.1). In section 5.2, the brain mechanisms underlying retrieval-induced forgetting are considered, which is when retrieval of one item (e.g., the word ‘banana’) has an inhibitory effect on related items (e.g., the word ‘orange’) and increases the rate of forgetting for these items. The brain regions associated with a related process called motivated forgetting, an increase in the rate of forgetting for items that one intentionally tries to forget, is then considered. In the next two sections of the chapter, 5.3 and 5.4, two types of memory distortion are considered: false memories (i.e., memories for information that did not occur) and flashbulb memories (i.e., seemingly picture-like memories for very surprising and consequential events). It has been argued that long-term memory failure reflects an adaptive memory system that works well (Schacter, 1999; Schacter, Guerin & St. Jacques, 2011).