Procedural learning - what is it and what does it have to do with dyslexia?

Procedural learning is the acquisition of a series of processes for the performance of a certain task.  The ability to learn sequences of actions helps us learn how to ride a bike, produce and perceive phoneme sequences, tie shoelaces, drive, play music and perform any activity with a serial aspect.  All these skills are acquired through lots of practice. 

The interesting thing about procedural learning and memory is that they can happen out of awareness.  That means that we learn to perceive regularities and sequences in the stimuli surrounding us, even when we are not aware of it and certainly don't pay attention and effort to it.

In this study done by Yafit  Gabay  , Rachel Schiff  and Eli Vakil of Bar Ilan university in Israel, procedural learning was examined with adults with dyslexia.

Dissociation between the procedural learning of letter names and motor sequences in developmental dyslexia.  Yafit  Gabay  , Rachel Schiff  , Eli Vakil.  Neuropsychologia 50 (2012) 2435–2441

The researchers used a procedure called serial search task.  University students with and without dyslexia saw four letters presented on a computer screen, and heard the name of one of the letters.  Upon hearing the letter name, they pressed one of four possible keys – the one that was in a corresponding position to the visual representation of the letter that was named. This was repeated again and again.  The order of letters presented on the screen changed each trial, and so did the letter that was named.   For half of the participants, the order of key presses created a specific recurrent motor sequence.  For the other half, the order of the letters named created a specific pattern.  The participants were not aware of the existence of a motor sequence or a letter sequence.

Both student groups, with and without dyslexia, implicitly learned the motor sequence.

How did the researchers know this?

During performance, the participant's reaction times for the motor sequence became shorter. This was one of the signs that they were learning the sequence even though they were not aware of it.  But when the specific motor sequence was changed to a random motor sequence, the participant's reaction times became longer.  When the motor sequence was reinstated, the reaction times became shorter again.

But students with dyslexia could not learn the letter name sequence!  Their reaction time for the letter name sequence did not become shorter, while the reaction time of students without  dyslexia did.  When the letter sequence was altered to a random sequence, the reaction time of the students without dyslexia became longer, while the reaction time of the students with dyslexia did not change.

What does that mean?  The authors interpret the results as showing that people with dyslexia have difficulties learning procedures with linguistic components.  This argument was supported in this study by a learning task that is outside awareness (implicit learning).  This finding is joined by findings from explicit learning tasks: children with specific language disability have a severe difficulty to repeat nonwords.  The difficulty mounts  as the number of syllables in a word rises.  Repeating nonwords is a task that requires serial processing with a linguistic component.  Learning to pronounce a new word is a procedural learning task. 

Difficulty with serial learning impacts the ability to acquire grammar.  This argument is also supported by an interesting procedural learning task:  artificial grammar learning.  In this task, a person memorizes sets of letter sequences that appear random, but are formed by a complicated set of rules (an "artificial grammar").  After the memorizing phase, the person is presented with new sets of letter sequences.  Some of the sequences are built by the "grammar" rules and some are not.  The person is asked to sort the new "words" into "grammatical" words and "nongrammatical" words.  Although people are usually unable to describe the sorting rule, and often say they are only guessing, they do succeed in sorting above chance level.  That means they have implicitly learned the "grammar".  It appears that children with dyslexia are not able to perform this sorting task.