Is this why, as shown in the studies, we generally tend to remember the positive episodes in our life better than the negative ones? Psychologists refer to this as a “positivity bias”. “If we question people who have been plunged into dramatic situations, like a war or extreme economic difficulties, we’re always surprised at their propensity to subsequently minimise the serious problems with which they have been faced”, the FNRS researcher points out. “Even if they didn’t have anything to heat themselves with in the middle of winter, they’ll say that ‘it wasn’t really that cold after all’.”

It is necessary to distinguish between intentional forgetting, i.e., the result of the desire not to remember certain things, and unintentional forgetting, linked, among other things, to interference or the gradual elimination of mnesic traces owing to the fact that the information isn’t refreshed and that it doesn’t regularly enter our thoughts. Undoubtedly, these two processes intervene in the positivity bias to varying degrees.

As Christine Bastin explains, the memories that endure in the long term are those that are meaningful in relation to our personal objectives, the ones that we have elaborated and that we have regularly recalled, thus ensuring their consolidation and their durability. However, they are still at risk from "distortions’" because, to a certain extent, we constantly "reinvent" our memory. “An event that struck us at a given moment will nevertheless be forgotten if we never recall it from our memory”, Christine Bastin insists. “Over time, there is a decline in the mnesic trace, owing to interferences among other things, resulting from the emergence of new information and the competition that takes place between the various memories, especially when they are very similar.”

Directed forgetting

Researchers from CRC and the Department of Cognitive and Behavioural Psychology at ULg recently decided to study the regions of the brain involved in intentional forgetting. This work, which was the subject of an article in the journal Plos One(1) in January 2012, was based on a "directed forgetting" task. In other words, it meant asking volunteers to forget certain pieces of information they had been given.

In concrete terms, 17 students aged between 20 and 32 years old (nine men and eight women) were presented with 100 six-letter words during a learning phase (memory encoding), which appeared for a second on a computer screen. Each time a word was shown, it was followed by an instruction which remained on the screen for three seconds. What was the instruction? For 50 words: “To be remembered", and for the other 50: “To be forgotten”, with the words set in random order. What were the participants asked to do? First of all, to mentally read each word and only remember those that were followed by the instruction “To be remembered”, and to forget the others. Furthermore, those conducting the experiment told a white lie and said that the next test would be a simple memory test relating to the words that had to be remembered.

(1) C. Bastin, D. Feyers, S. Majerus, E. Balteau, C. Degueldre, A. Luxen, P. Maquet, E. Salmon, F. Collette, The Neural Substrates of Memory Suppression : A fMRI Exploration of Directed Forgetting, in Plos One, january 2012, volume 7, Issue 1, e29905.