When passives are easier than actives: two case studies of aphasic comprehension.

We outline a range of previous theoretical accounts of agrammatic comprehension in patients with Broca's aphasia. Specific attention is paid to patterns of preserved and impaired understanding of reversible actives and passives. We note that no prior account will allow for the existence of patients who show better comprehension of passives than actives. In three experiments, we compare and contrast the performance of two patients whose syntactic comprehension ability is in complementary distribution. The first patient (M.H.) performs well on simple actives, active questions, and active existentials, but is below chance on their corresponding passives. The second patient (B.M.) is at chance on simple actives, active questions and active existentials while scoring significantly above chance on their respective passives. We interpret both patterns of response in terms of the distinction drawn by Case theory between structural and inherent Case. The first patient's grammar cannot assign either structural or inherent Case and she must accordingly apply a non-linguistic linear strategy to assign thematic roles in all sentences. The second patient (B.M.) has a specific impairment of structural Case; he can accordingly not interpret actives (where Case is assigned configurationally) but can interpret passives (where Case is assigned lexically).