During the frequency-discrimination task, participants were asked to compare two tones in each trial. All participants’ responses were affected, or biased, by implicit memory of previous stimuli. Both groups were affected in similar ways by very recent stimuli, but dyslexics were less affected by earlier stimuli.
“This suggests that implicit memory decays faster among dyslexics,” said Jaffe-Dax.
“We decided to test this hypothesis by increasing the length of time between consecutive stimuli and measuring how it affects behavioral biases and neural responses from the auditory cortex, a section of the brain that processes sound.
“Participants with dyslexia showed a faster decay of implicit memory on both measures. This also affected their oral reading rate, which decreased faster as a result of the time interval between reading the same nonword — a group of letters that looks or sounds like a word — numerous times.”
The team concludes that dyslexics’ faster recovery from stimuli can account for their longer reading times, as it causes less reliable predictions for both simple and complex stimuli.