Turning to our patients' performance in the whole report experiment (Experiment 2), the most notable finding is that all patients had severely reduced visual apprehension span compared with normal controls, and that this reduction was not specific to letters in any patient.
Visual apprehension span was also reduced for both letters and digits in all patients.
In addition, visual apprehension span (K) was markedly reduced in all patients (Experiment 2).
TJ's performance showed the same pattern in both visual fields, his visual apprehension span (K) was significantly reduced for both letters and digits (P < 0.001, Crawford and Garthwaite's test), whereas his processing speed (Cperipheral) was not significantly different from controls in this individual comparison.
This corresponds to the TVA parameter K, the visual apprehension span.
Two parameters are of special interest in the present investigation, the speed of visual processing C and the visual apprehension span K.
With regards to estimates of visual apprehension span, K, patients differed significantly from controls both for letters and digits on a group level as well as individually.
For each stimulus type 2 main parameters were estimated: visual apprehension span, K, and visual processing speed, Cperipheral (defined as the sum of the processing speeds at each of the 5 stimulus locations).
Whole report paradigms, where subjects have to report elements from a display of multiple, unrelated stimuli (usually 5) also allow for the estimation of K the visual apprehension span.
Two measures of visual capacity, "processing speed" (the number of items processed per second) and the "visual apprehension span" (the maximum number of items that can be recognized in one view), can be modeled within this framework, and these 2 parameters can be assessed for different stimulus types.
