Remember for a moment a recent gathering with friends. Who was there? When and where did the event take place? Now imagine a future gathering with friends. Who is there? When and where does the event take place? As with mentally reliving the past, mental representations of the future include images of personal episodes taking place in specific settings.
According to cognitive psychologist Endel Tulving, Ph.D., the ability to envision specific future scenarios (called episodic future thought) may be closely related to the ability to recollect specific episodes from our past (that is, episodic memory). Indeed, evidence from neuropsychology, clinical psychology, and developmental psychology indicates that people who cannot remember specific details from their past also appear to be impaired in their ability to mentally envision personal future experiences.
Efforts to understand the relationship between memory and future thought are in their infancy. The potential payoff, however, is considerable: it will likely inform our basic understanding of human memory, as well as of brain disorders in which that most essential human ability is impaired.
Evidence from Damaged Brains
Consider the patient known in the scientific literature as KC. KC, who has been studied extensively by Tulving and his colleagues at the University of Toronto,1 has global amnesia caused by diffuse brain damage that he sustained in a motorcycle accident. Many of KC’s cognitive abilities are intact, but he can neither remember any single episode from his past nor project himself mentally into the future. When asked to do either, he states that his mind is “blank”; when asked to compare the kinds of blankness in the two situations, he says it is the “same kind of blankness.”
DB, another brain-injured patient who has been studied by Stanley Klein, Ph.D., and his colleagues at the University of California at Santa Barbara, exhibits a similar profile. Following DB's cardiac arrest, his brain sustained damage due to lack of oxygen. DB can no longer recollect his past, nor can he project himself into the future.2 Both KC and DB have self-concepts consistent with descriptions An inability to envision a “brighter future” may contribute to sustaining depression. of their personalities given by others who know them well. Although they cannot remember specific events from their own pasts, their overall self-knowledge (for example, “I am generally comfortable in social settings”) is reliable and can even be changed by new experiences. Moreover, both patients understand the concept of time: they know that there is a future and a past, they can tell time with an analog clock, and they know about their past and their future in a vague sense. What they lack is the ability to perform mental time travel.
Eleanor Maguire, Ph.D., and her colleagues at University College, London, have recently replicated what was observed with KC and DB and extended the observations in a more systematic fashion.3 Five amnesic patients were tested for their ability to form mental images of novel experiences that might take place in the future in a familiar setting, such as a possible event in their lives over the next weekend. These patients were markedly impaired in their ability to do this—their mental images were vague and highly fragmented when compared to those reported by a control group of people of the same average age and level of education but without amnesia.
Another example can be found in people with severe depression. Researchers have known for some time that such individuals have difficulty in bringing to mind personal details from their past. Mark Williams, Ph.D., and his colleagues at the University of Wales showed in 1996 that people with clinical depression are also impaired in their ability to engage in episodic future thought, a discovery that may have important implications for understanding how prolonged depressive states are maintained. For example, an inability to envision a “brighter future” may contribute to sustaining depression.