Daydreaming is a critical component of conscious experience. The mind can perform mental time travel – it occasionally strays from the present moment, to recollect an experience from the near or distant past, or to imagine an event that has not yet taken place. We know that thinking about the future is dependant on memory, because patients with amnesia cannot imagine new experiences. It involves piecing together fragments of past experiences to generate a plausible simulation of what might happen. This may have been an important development in human evolution, as it enables us anticipate a likely outcome and to plan the best possible course of action.
Space and time are intimately linked in the mind, and this is reflected in our metaphors. We often say that we are thinking back to a past event, or looking forward to one that will take place in the future. But the mind and body are also closely linked: think about a past experience, and you might find yourself moving backwards. A new study suggests that this can be reversed, by showing that apparent motion can influence the direction of the mind’s wanderings. Thus, moving backwards could evoke long lost memories, while moving forward might make you think about the future.
Psychologist Lynden Miles and his colleagues at the University of Aberdeen’s Social Cognition Lab recruited 26 undergraduates, and told them that the experiment was designed to investigate vigilance in a dynamic environment. The participants were asked to sit in front of a large screen, on which they were shown an animated pattern consisting of about a thousand white dots positioned randomly on a black background. For one group of participants, the dots moved towards the centre of the screen, to simulate forward movement. For the other, the dots moved in the opposite direction, giving the impression of backward movement.
The participants were required to monitor these moving displays for specific targets, and told to click the mouse button as quickly as possible whenever they detected one of the target, but to withhold clicking when they saw the other. But the designated targets were rare, appearing just six times during each 6-minute display. The task was designed to be mundane, in order to increase the likelihood that the participants’ thoughts would wander while they performed it.
Afterwards, the participants were asked if they had experienced any unrelated thoughts while they viewed the display. The 25 who reported that they had daydreamed during the task were asked to dismiss those thoughts that were anchored in the present moment, and to consider only those that related to the past or future. They were then asked to indicate the proportion of past- and future-related daydreams on a horizontal line. If, for example, their thoughts consisted solely of daydreams related to the past, they were to mark the extreme left end of the scale.
Remarkably, it was found that the direction of illusory motion in the moving displays modulated the direction of the participants’ mental time travel. Those participants who had viewed the display with apparent backward motion reported that the daydreams they had experienced during the task consisted mainly, or solely, of memories of the past, while those who viewed the display with apparent forward motion reported thoughts related to the future. The displays used in the study produced an illusory sense of motion, so real movements could possibly have a stronger effect.
Last month, Dutch researchers reported that bodily motion influences the emotional content of recalled memories, and Miles and his colleagues have previously demonstrated that mental time travel is associated with physical movements through space. In a study published in January, they showed that past thoughts are linked to backward movements, and future thoughts to forward movements. The new findings show that the reverse is also true: apparent movement through space influenced the temporal focus of the participants’ thoughts. This all suggests that the capacity of mental time travel is firmly grounded in physical representations of space, and that the relationship between the two is reciprocal and bi-directional.
The way in which the mind integrates abstract concepts of time and concrete representations of space may be influenced by cultural factors. When mapping time onto space, we often think of events that have not yet occurred as being located in front of the body, whereas those which have already passed are thought of as being located behind. This is reflected in metaphors such as looking forward, but this is not true for everyone. In the Aymara ethnic group of the Andes and Altiplano regions of South America, for example, the mental relationship between space and time is reversed. By convention, Aymara speakers refer to past (or known) events as being located at the fore, and future (unknown) events as being behind, so the way in which movements influence the direction of mental time travel may also be reversed.
- Mental time travel
- Bodily motions influence memory and emotions
- The cognitive benefits of time-space synaesthesia
- Reconstructive memory: Confabulating the past, simulating the future
- Does time dilate during a threatening situation?
Miles, L. K., et al (2010). The Meandering Mind: Vection and Mental Time Travel. PLoS One 5 (5): e10825. doi:10.1371/ journal.pone.0010825. [Full text]
Schacter, D. L, et al (2007). Remembering the past to imagine the future: the prospective brain. Nat. Rev. Neurosci. 8: 657-661. [PDF]