Suddendorf & Corballis (S&C) convincingly argue that memories of past events and images of future ones are not literal representations of the past and future, but are instead the products of generative, constructive processes that (re)create mental representations by (re)arranging pieces of information retrieved from memory (see also Schacter & Addis Reference Schacter and Addis2007a). The resulting representations can therefore be highly selective, and the pieces of information that are encoded, maintained, and retrieved from memory in priority are those that are most relevant to an individual's goals, beliefs, and concerns (Conway Reference Conway2005). Emotion plays an important role in this selection process, as it signals the occurrence of information that has potentially important implications with regard to goals (Ellsworth & Scherer Reference Ellsworth, Scherer, Davidson, Scherer and Goldsmith2003). Consequently, emotional stimuli are typically remembered with more details than neutral stimuli (D'Argembeau & Van der Linden Reference D'Argembeau and Van der Linden2005; Kensinger et al. Reference Kensinger, Garoff-Eaton and Schacter2006), and autobiographical memories for emotional events are associated with a higher subjective feeling of mentally reliving the past (D'Argembeau et al. Reference D'Argembeau, Comblain and Van der Linden2003; Talarico et al. Reference Talarico, LaBar and Rubin2004). In addition, for both past and future, representations of positive events are associated with a greater feeling of re-experiencing (or pre-experiencing) than representations of negative events (D'Argembeau & Van der Linden Reference D'Argembeau and Van der Linden2004). In this commentary, we would therefore like to suggest that humans accord a privileged status to emotional information when they mentally travel backward or forward in time, and we consider some reasons why this might be the case.

S&C argue that the primary function of mental time travel is to enhance biological fitness in the future: Mentally simulating various versions of the future, and their respective consequences, enables one to act flexibly in the present to increase one's future survival chances. We completely agree, and would add that the affective charge of the generated mental images is a key element in this respect, the driving force that guides our current decisions. Affective states associated with mental simulations of positive and negative outcomes motivate us to engage in certain types of behaviors (e.g., start a diet) and to avoid others (e.g., quit smoking), in order to maximize the probability of attaining our goals. Future rewards and punishments need not be consciously represented to guide decision making (Bechara & Damasio Reference Bechara and Damasio2005), but the conscious mental simulation of emotional situations, through mental time travel, undoubtedly provides unique information that promotes successful adaptation to life circumstances. Negative memories remind people of their past errors and provide cues on how to avoid undesired outcomes or minimize their consequences, whereas positive memories remind people of their past accomplishments and provide cues on how to attain success. These pieces of information regarding the personal past can be used to generate representations of the future that specify (a) which situations should be approached or avoided, and (b) how to maximize the probability of attaining/avoiding them. Mental imagery, especially visual imagery, may play a particularly important role in representing such goal-related information, as it is a sort of “language” of goals (Conway et al. Reference Conway, Meares and Standart2004). Interestingly, it has been found that people who have higher visual imagery capacities generate more detailed representations of their personal past and future, and rate their representations of future events as being more emotional and meaningful (D'Argembeau & Van der Linden Reference D'Argembeau and Van der Linden2006). It would be interesting to investigate whether these individual differences are correlated with the ability to make adaptive decisions. Alternatively, the ability to envision detailed emotional past and future events should be explored in individuals who show impairments in judgment and decision-making in real-life settings, such as patients with lesions of the ventromedial prefrontal cortex (see Bechara & Damasio Reference Bechara and Damasio2005).

Although the primary function of emotional aspects of mental time travel may be to help one make adaptive decisions, mental representations of emotional episodes probably serve other functions as well. Representations of emotional events induce significant modifications of emotional responses and feelings (Damasio et al. Reference Damasio, Grabowski, Bechara, Damasio, Ponto, Parvizi and Hichwa2000), and may therefore be used to regulate affective states. Sometimes we remember or imagine positive experiences, not so much to help us make decisions or plan future actions, but simply to feel better in the present. There is evidence that people occasionally retrieve positive events in order to repair a negative mood (McFarland & Buehler Reference McFarland and Buehler1998). Note that the use of mental simulations to regulate mood states is not always straightforward, however; people probably use rather complex strategies that may vary across situations. For example, one may strive to generate or prolong a positive affective state by envisioning negative events (e.g., how things might be worse), which allows one to feel good in comparison (Sanna Reference Sanna2000).

Finally, a third function of the emotional aspects of mental time travel may be to provide material to support representations of the self. Most people hold positive views of themselves and are more willing to consider information that bolsters their self-image than information that contradicts it (Baumeister Reference Baumeister, Gilbert, Fiske and Lindzey1998). Thus, memory tends to be biased toward confirming positive self-views. For example, as mentioned earlier, positive episodes are subjectively experienced with more details and with stronger feelings of (re)living than negative episodes, for both the past and the future (D'Argembeau & Van der Linden Reference D'Argembeau and Van der Linden2004). In addition, when asked to think about their future, people spontaneously imagine more positive than negative events (Newby-Clark & Ross Reference Newby-Clark and Ross2003) and judge positive events as being more likely to happen (Weinstein Reference Weinstein1980). The importance of the balance between positive and negative future thinking is further revealed by its disturbance in certain psychopathological conditions. For example, depressed individuals tend to generate fewer positive future events, while anxious individuals tend to generate more negative future experiences (MacLeod & Byrne Reference MacLeod and Byrne1996). Positive biases in representing the past and future probably help maintain a positive view of the self and foster optimism concerning one's personal future, which may promote physical and mental health (Taylor & Brown Reference Taylor and Brown1988).