A man is the sum of his memories, you know, a Time Lord even more so.

The Doctor, in “The Five Doctors”

We all know that our memories can’t always be trusted, time and life tends to erode the confidence we have in our memories. At least that is the case for normal memories. We also tend to have special memories that seem to be burned into our brains, events in our lives that hold such significance that it feels like we are in some sense still experiencing the moment the memory represents. Such memories are described as being “flashbulb memories” as if at that moment as sort of metaphysical flash went off and recorded every detail of an event vividly in our consciousness.

This “flashbulb” effect allows us to confidently recall these events days, weeks or even years later. Memories such as this may be unique to each individual but there are commonly cited examples of shared flashbulb memories such as where a person was and what they were doing when they heard about the events of 9/11. In fact this event was used in an experiment to test the accuracy of this type of memory. At Duke University on September 12th 2001, 54 students recorded their memories of hearing about the incident as well as a recent everyday event by answering a series of questions about the events. Then either 1, 6 or 32 weeks later they answered another questionnaire and this was used to evaluate the confidence and consistency of the memories.

Surprisingly there was no difference in the consistency of memory recall for the flashbulb memory compared to the everyday memory but the flashbulb memory continued to be reported with a high degree of confidence while confidence in the everyday memory decreased. This implies that while we can be very confident in the details of a memory this is no guarantee of their accuracy. In fact other studies between confidence and accuracy of recall (for example in eye witness reports of crimes) shows the same lack of correlation between how confident we are and how accurately our recall matches events.

With regard to confidence in memories hypnosis is often put forward as a means of increasing the reliability of recall (even featuring on Mythbusters). There is evidence however that what actually happens is the hypnosis increases the confidence of the recall but is not effective at increasing the accuracy of the information gained through this process.

Finally, as a little reward for getting this far that is modestly related to this subject, here’s an interesting little test that is meant to measure your risk IQ based on your confidence in the answers to certain questions rather than on the answers themselves. (as previously blogged on by Alison over on Bioblog). So go take the test and feel free to report back your score.


Talarico, J., & Rubin, D. (2003). Confidence, Not Consistency, Characterizes Flashbulb Memories Psychological Science, 14 (5), 455-461 DOI: 10.1111/1467-9280.02453
Smith, V., Kassin, S., & Ellsworth, P. (1989). Eyewitness accuracy and confidence: Within- versus between-subjects correlations. Journal of Applied Psychology, 74 (2), 356-359 DOI: 10.1037/0021-9010.74.2.356
Green, J., & Lynn, S. (2005). Hypnosis versus relaxation: accuracy and confidence in dating international news events Applied Cognitive Psychology, 19 (6), 679-691 DOI: 10.1002/acp.1133

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