Research: Dyslexics have better picture-memory (updated)

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(Researchers puzzled by results)

If you wanted to design a study to test the hypotheses that dyslexics tend to think in pictures rather than words, one way to do that would be to test them on their ability to remember pictures that they have seen. You might guess that picture-thinkers would tend to store and retrieve remembered images more readily than non-dyslexics. If there is a system in the brain for retrieval,a picture-thinker would be more likely to associate images with visual qualities such as size, shape, or color,  or an understanding of what the image depicts, rather than object names.

So I was delighted to see the recent publication of a study with the title Enhanced Recognition Memory … in Children with Developmental Dyslexia. Cool, I thought – researchers who are focused on studying a dyslexic gift. 

I was even happier, when I read the study, to see that the results were exactly as I had anticipated. The researchers compared the performance of  group of 11-year-old dyslexic children with a group non-dyslexic children on tests of how well they remembered line drawings 10 minutes and 24 hours after first being shown the pictures. As I would anticipate, the dyslexic children performed significantly better on those tests of visual memory.

The results are quite clear. Dyslexic children are marginally faster at distinguishing whether drawings depict real vs. imaginary objects, and much better at remembering whether they have seen a picture before.

But apparently that was not the result the researchers expected to see. They had hypothesized that both groups of children would perform about the same.

Why? Because they thought they were studying declarative memory (memory of factual knowledge and personally experienced events), not picture-thinking. I suppose they used pictures in their memory test simply because they could not expect children with known reading difficulties to remember words.

Here’s how they explained their goals:

The aim of the present study was to investigate a previously untested aspect of declarative memory in children with DD [developmental dyslexia], namely recognition memory after incidental encoding. Based on previous evidence indicating that declarative memory impairments in DD may be related to less efficient encoding strategies  and/or problems with free recall, we predicted that the present paradigm would yield intact performance in the DD group.

In other words, they wanted to test memory in dyslexic children without needing to rely on the ability to remember or recall words.  So they expected that once they eliminated word-memory from the experimental setting, dyslexics would perform about the same as other children.

So they were puzzled when it turned out that the dyslexic children were so much better at remembering the pictures.  That led them to propose three different, rather convoluted, reasons for the disparity in ability:

Researcher suggestion #1: Maybe dyslexic children are better at making up new labels in their brains for things they see, to compensate for their “lexical retrieval deficits.”  Then when they see the objects again, they have their new labels available to jar their memory.

Researcher suggestion #2: Maybe the dyslexic children were simply normal in their ability to remember pictures, but the non-dyslexic group was impaired because the process of learning to read required them to use up space in their brains to remember sight words, thus reducing the available memory available for remembering other stuff they saw.

Researcher suggestion #3: Maybe the declarative memory (conscious memory for facts and experiences) is improved in dyslexia as a way to compensate for deficits in procedural memory (subconscious memory based on  repetition and practice) is impaired. 

I think it’s a good thing when researchers try to explore multiple possible explanations for results.

But I am puzzled as to why the researchers don’t even mention the obvious: maybe dyslexics just store memories of images in their minds better than non-dyslexics.

When I store pictures on my computer hard drive, I can look for them in two ways: I can look through a list of their file names, or I can look through a folder with thumbnails of the images.  I usually find it much, much easier to look at the pictures than to try to remember the file names.

I don’t get it. I understand that there are some people in this world who aren’t very good at mental imagery. But this dyslexia study has five named authors — is there not a single one who has figured out the visual memory calls upon different mental resources than the memory for things heard or for abstract ideas?  That rather than looking at “declarative memory” as a bucket in which all items that can be consciously recalled are lumped together, that we as humans may use very different neural networks when asked to recall something that we have seen as opposed to, say, something that we  touched or something that we smelled?   That you  can’t draw a conclusion about “declarative memory” without first accounting for the smaller subset  memories that correlate to different sensory perceptions?

I am glad that these researchers conducted this study, and I am glad that they have published it in an open access journal. But I just wish they could have tried to see the picture that was right in front of their eyes.

Here’s the citation and link to the study:

Enhanced Recognition Memory after Incidental Encoding in Children with Developmental Dyslexia Hedenius M, Ullman MT, Alm P, Jennische M, Persson J (2013) PLoS ONE 8(5): e63998. doi:10.1371/journal.pone.0063998

Research Update: More recently, scientists using diffusion MRI to map the brain connections in children have shown that children with word recognition difficulties consistent with dyslexia have greater brain connectivity to the visual cortex and parahippocampal region, which is tied to memory and memory retrieval. The children with good reading skills had stronger connections with the linguistic regions of the brain including Visual Word Form Area. In other words, the brains of dyslexic kids are wired for better memory of pictures than words. Citation: Structural connectivity patterns associated with the putative visual word form area and children׳s reading ability. Qiuyun Fan, Adam W. Anderson, Nicole Davis, Laurie E. Cutting (2014) Brain Research,
1586: 118-129, doi: 10.1016/j.brainres.2014.08.050 (Full Text)

This article was originally published on 28 May 2013 and updated with new information about a subsequent study on 29 March 2019.