Figure 8. Extra letter spacing improves comprehension in those most impaired.

The shape of the interaction of Crowding and reading levels for FIDELITY, a measure of reading comprehension, is plotted. A significant interaction of Crowding*High Reading was observed when FIDELITY was taken as the dependent variable. Degree of Reading Power (DRP) scores for each student, an a priori measure of their overall reading level, was used to create a dummy variable (High Reading) used to divide participants into high and low reading level groups. Those with high reading levels read well with either spaced or normal text, however, those most impaired read more effectively in the spaced condition. (Error bars indicate +/−1 s.e.)