Do children with a specific reading disability have a general serial-ordering deficit?

Two experiments are described in which reading disabled subjects and their normal controls were tested for their ability to abstract sequential regularities from a noisy background. Subjects were presented with an adaptation of the repeated digits task of Hebb (1961) and its spatial analogue the Corsi Blocks (Milner, B. Br. Med. Bull. 27, 272-277, 1971). Normal subjects had a digit span significantly better than their block span and also significantly better than that of the disabled readers. This suggested that normal subjects have better defined "storage filters" for digits or a specific advantage in the construction of 'transitory filters' for verbal material. There were no differences between groups on block span. On the repeated digit sequences normal readers abstracted a relatively stable "storage filter" in the first five recurrent trials whereas the disabled readers showed no discrimination until the last five recurrent trials. On the repeated blocks task the disabled group performed as well as normal readers. Taken together this date gives strong evidence for a specific deficit in verbal serial organization in disabled readers but does not support a general deficit in serial organization.