This six hour time period is what experts call a “reconsolidation window” and is basically a time period during which bad can be changed to good.
A team at New York University found that they were able to erase bad memories if they acted within six hours and they hope that in the future this discovery will help those with disorders such as post traumatic stress.
The study involved the volunteers being wired up to electrodes which delivered a shock each time they were shown a picture of differently coloured squares to make them fear certain images.
The day after the shocks were delivered the researchers attempted to banish the fear by re-exposing the volunteers to the same images but this time minus the shocks.
This technique was found to work but only in the event that the volunteer recalled the fearful image no longer than six hours before the treatment commenced.
Lead researcher Dr Elizabeth Phelps of New York University said: “Timing may have a more important role in the control of fear than previously appreciated.