Impaired motor timing control in specific reading retardation.

The temporal organizations of unimanual and coordinated bimanual finger tapping was compared between adolescent normal and retarded readers of above average intelligence. The same subjects were examined for speech articulation during the timed repetition of single syllables and syllable sequences. Retarded readers had substantially greater difficulty on tasks of interlimb coordination than on unimanual tapping and substantially greater difficulty rapidly sequencing syllable strings than repeating single syllables. An experimental manipulation of movement speed for both tasks indicated that the threshold at which movement speed degrades timing precision for coordinated action best characterizes the motor impairment of retarded readers.