“Broca’s area is adjacent to the part of the motor-control strip dedicated to the jaws, lip, and tongue, and it was once thought that Broca’s area is involved in the production of language (though obviously not speech per se, because writing and signing are just as affected). But the area seems to be implicated in grammatical processing in general. A defect in grammar will be most obvious in the output, because any slip will lead to a sentence that is conspicuously defective. Comprehension, on the other hand, can often exploit the redundancy in speech to come up with sensible interpretations with little in the way of actual parsing. For example, one can understand The dog bit the man or The apple that the boy is eating is red just by knowing that dogs bite men, boys eat apples, and apples are red. Even The car pushes the truck can be guessed at because the cause is mentioned before the effect. For a century, Broca’s aphasics fooled neurologists by using shortcuts. Their trickery was finally unmasked when psycholinguists asked them to act out sentences that could be understood only by their syntax, like The car is pushed by the truck or The girl whom the boy is pushing is tall. The patients gave the correct interpretation half the time and its opposite half the time—a mental coin flip.”