People with no mind’s eye have less vivid and detailed memories

When we're asked to imagine a scene or object, most of us are able to conjure up an image in our mind's eye. But about 2-5% of the population can't do this: they have a condition called aphantasia, and are unable to produce mental imagery at all.

Now a study published in Cognition has found that aphantasia can affect memory abilities too. The researchers report that aphantasics have less detailed and rich memories for events in their lives: a finding that not only reveals more about the condition, but also highlights the key role of mental imagery in memory generally.

Past work had shown that people with aphantasia report almost no mental imagery when recalling past events from their lives or when thinking about potential future events. But these findings were based on participants rating their own abilities, note Alexei Dawes and colleagues from the University of New South Wales. So the team decided to examine whether aphantasic participants also show memory deficits in more objective measures.

The researchers recruited 30 participants with aphantasia and 30 control participants who didn't have any problems with mental imagery.  All participants filled in questionnaires asking them to report the vividness off various kinds of mental imagery, including when recalling scenes from their lives. The researchers found that — as in past studies — the aphantasic participants reported having less vivid mental imagery (although, again consistent with past work, their spatial imagery was just as good as that of control participants).

To get a more "objective" measure of memory deficits, the team then looked at the kind of information people provided when describing their memories. Participants were asked to remember six events in their lives, as well as think about six hypothetical future events, and write a description of each. For their analysis, the researchers looked at different categories of details contained in these descriptions (for instance, details relating to participants' sensations, thoughts, or emotions). After writing each description, participants also reported their own subjective experiences of that particular event, such as how vivid it was and how much emotion they felt.

The team found that aphantasic participants gave fewer details than control participants about both kinds of event. This effect seemed to be driven specifically by the fact that they wrote down fewer visual details; the groups didn't differ in the amount of detail they gave that involved other senses like smell or hearing, or that concerned other aspects of the event like thoughts or emotions they experienced.

The two groups also differed in how they reported experiencing the memories and imagining the future events. Compared to controls, aphantasics indicated that the events were less vivid and contained fewer sensory or spatial details, for instance, and they also reported experiencing less emotion when thinking about the event.

Overall, the results show that people with aphantasia have less vivid and detailed memories — particularly when it comes to visual details — and this this effect is clear whether they are asked about their experience or tested in more "objective" ways. The authors write that their findings represent the "first robust behavioural evidence that visual imagery absence is associated with a significantly reduced capacity to simulate the past and construct the future".

The very fact that aphantasics show these deficits also implies that mental imagery is generally an important part of recalling events or imagining future ones. This probably isn't a huge surprise — but as the authors point out, is something that has been hard to test empirically until now. However, the study also shows that mental imagery isn't everything: people with aphantasia were still able to retrieve memories, after all. Instead, it seems that mental imagery is specifically involved in that aspect of memory that involves "re-living" events in our minds.

• Matthew Warren (@MattBWarren) is Editor of BPS Research Digest