Figure 7.

Schematic diagram of flow of computation for: (A) unidirectional procedure for calculating the posterior probabilities of letters in the first position and (B) bi-directional procedure for calculating the posterior probabilities of all four letters. The dashed ovals highlight the differences between the two procedures. In the unidirectional procedure, calculation proceeds upwards to the word level from positions 2, 3, and 4, and downward only for position 1. In the interactive procedure, calculation proceeds upwards and downwards in all four positions.