The assumption that we human beings can control and intentionally forget unwanted memories has been controversial ever since Freud asserted it at the beginning of the 20th century. Now, psychology researcher Gerd Thomas Waldhauser has shown in neuroimaging studies that Freud was correct in his assumptions: in the same way as we can control our motor impulses (we can for example rapidly instruct the brain not to catch a cactus which is falling from a table), we can control our memory.
Waldhauser's tests are carried out in a laboratory environment where volunteers are asked to practise forgetting, or attempting to forget facts. Through EEG measurements, Waldhauser shows that the same parts of the brain are activated when we restrain a motor impulse and when we suppress a memory. And just as we can practise restraining motor impulses, we can also train ourselves to repress memories, i.e. to forget.
Waldhauser points out several situations in which forgetting could be helpful. People suffering from depression often dwell on negative thoughts which might best be repressed or forgotten in order for the individual to emerge from the depression. The same thing goes for people with post-traumatic stress disorder; the trauma makes it difficult for the affected person to act rationally and to resolve his or her situation. But the possible consequences of a deliberate repression of memories are still not clearly established.
"We know that 'forgotten' or repressed feelings often manifest themselves as physiological reactions", says Waldhauser, who is careful to point out that the volunteers were trained to forget neutral information in a controlled laboratory environment. Training to forget a traumatic event would be more complex.
Waldhauser has not only shown that we can deliberately forget things. Through EEG measurements, he has also managed to capture the exact moment when the memory is inhibited, that is when the forgetfulness is imposed.
The inhibition of memory eases off after a few hours. But the more often information is suppressed, the more difficult it becomes to retrieve it, as Waldhauser has shown through studies in a laboratory environment.
"If the memories have been suppressed over a long period of time, they could be extremely difficult to retrieve", says Waldhauser.
Gerd Thomas Waldhauser has publicly defended his doctoral thesis, Behavioral and Electrophysiological Correlates of Inhibition in Episodic Memory.
He can be reached at gerd.waldhauser@psychology.lu.se or on his telephone +46-46-2223638