A recent article in Trends in Cognitive Sciences summarizes the current knowledge about the individual differences in autobiographical memory.
Autobiographical memory includes every piece of knowledge related to the events of a person’s life. As most cognitive abilities, autobiographical memory may also differ between individuals. Recently two phenomena came under scrutiny which vividly illustrate this, highly superior autobiographical memory (HSAM) represents the upper, and severely deficient autobiographical memory (SDAM) represents the lower end of the autobiographical memory spectrum.
The first case of highly superior autobiographical memory was described in 2006, when a woman aged 41 contacted a prominent memory researcher. She was able to recall with great detail almost every day of her life, from the age of 11. Although generic tests measuring autobiographical memory are hard to verify, the correct dating of major world events and detailed description of life events may be considered valid demonstrations of HSAM. It should be noted that many of the people who claimed to have this condition failed to perform as required on these tests, and currently only around a 100 cases are considered valid presentations of HSAM. People with HSAM perform in the average range in standard cognitive tests, but there are some reports of higher scores on memory tasks, although the difference is not as emphatic as would be expected. SDAM on the other hand, presents with a decreased ability to recall autobiographical events, but they usually also score in the normal range on tests of cognition. This condition is even more difficult to verify, as affected people may produce autobiographical details of their lives based on their factual knowledge without any episodic recollection.
Since the topic is relatively new, experimental data on these conditions are scarce. Some brain imaging studies showed differences in temporal lobe structure and connectivity with other areas, and this is consistent with the proposed role of the temporal lobe in autobiographical memory. Autobiographical memory involves perceptual and self-referential processes, and these were also considered in the context of HSAM and SDAM. For example, SDAM is frequently associated with aphantasia, the lack of visual imagination, and this may well be the root of their deficit. Some people affected with HSAM, show a near obsessive interest in their personal past which suggests a link with self-referential processes. Thus, there are some hints that anatomical differences may underlie these extremes of autobiographical memory ability and there are also some links to other aspects of cognition, however these should be considered preliminary at best.
In sum, HSAM and SDAM are considered to be worthy topics for future experimental studies. The authors suggest that staged events may be useful in assessing the detail of recollection in future studies. These studies would assess the recollection of an event arranged by the experimenters in a laboratory setting so every detail could be verified. This is an interesting area, with a lot of potential to have an impact on our understanding of human memory and its relation to other aspects of cognition.