Can you imagine being able to remember every single day of your life? This is the case for people with highly superior autobiographical memory (HSAM) – an extremely rare condition which affects fewer than 100 people in the world.
In contrast to the majority of us, who can probably recall some details about what we’ve been doing on specific days for the last fortnight or so, people with HSAM can do this for years, and some even right back to when they were a baby.
The first recorded case of HSAM was in a woman called Jill Price in 2000, by memory specialist Dr James McGaugh at the University of California. Jill could remember every day of her life in detail, back until she was 14 years old. She knows what happened on any given date and what day of the week it was, right down to specific details like sounds and smell. She believes her extraordinary memory was triggered by her and her family moving to a different part of the USA when she was 8 – she was anxious about forgetting things about her old life and after this period, found her memory had changed.
However, just because people with HSAM can remember every detail about what has happened in their lives, this doesn’t mean that they have a superior memory when it comes to other types of information. For a quick recap – our long term memories are divided into 3 main groups: episodic – personal information about us e.g. memories of what we did for our birthday last year, or our experience of school when we were little; semantic – facts e.g. knowing the year London held the Olympics or the capital city of Spain. The third category is procedural memory, which is memory for actions e.g. how to ride a bike (for more information see this blog post). People with HSAM have extraordinary episodic memory, but they perform similarly to the general population on tests which involve the other two – they have no greater capacity to remember facts or memorise large amounts of information than we do. Another study has shown that they are more susceptible than control participants to a task which aims to plant false memories (Patihis et al, 2013) – so their memory is still as unreliable as ours.
How people with HSAM encode memories has also been tested, and the authors of the study (Leport et al, 2017) concluded that they seem to create memories in exactly the same way as the general population. This, added to the results of the false memory test seems to suggest that there isn’t something special about the way memories of people with HSAM are made which means they can remember more. The current hypothesis is that it is something in between encoding and retrieval which makes their memory so special.
The brain structure of people with HSAM has been investigated using fMRI, with images showing that people with the condition have differences to the parahippocampal gyrus, anterior insula and temporal gyrus. (LePort et al, 2012). Previous research has shown that these areas are involved in autobiographical memory, so this result perhaps isn’t surprising. There was also evidence of improved coherence in the white matter tract which connects the two hemispheres, suggesting a superior ability to transfer information between different parts of the brain. However, this study alone is not enough to show whether these differences were caused by the advanced memory capabilities of these participants, or whether they are a result of them remembering so much information.
Although having perfect memory might seem to be an advantage, people will this condition can often struggle with the sheer amount of information they can remember. Memories are often described as intrusive, popping up when they see anything which reminds them of something in the past. Jill Price says that she perceives a ‘split screen’, with the present happening on the left, and a constant stream of memories on the right. Having the ‘perfect memory’ might be more trouble than it’s worth.