Bias of quantifier scope interpretation is attenuated in normal aging and semantic dementia

Many sentences with two quantifiers exhibit a phenomenon known as “quantifier scope ambiguity.” Consider the example A unicorn ran through every garden, which contains the quantifiers “a” and “every.” Most speakers of English agree that it may refer to one or more than one unicorn. Very little previous work has evaluated the ability of brain-damaged or aphasic patients to interpret such sentences. We administered a sentence-reading task with picture verification to a group of semantic dementia patients (N = 5) and a matched group of cognitively normal controls (N = 23). Controls exhibited a tendency to interpret the word every as having wide scope regardless of the order of quantifiers, as evidenced by decreased reaction time and increased accuracy when verifying pictures that required this interpretation. This bias was attenuated by increasing age and by the presence of semantic dementia. Furthermore, higher FAS fluency scores were associated with slower responses and more errors, while higher semantic fluency scores were associated with the opposite pattern. These findings fit best with a model in which the initial products of linguistic analysis are underspecified and biases in their interpretation arise subsequently through frontally mediated logical or pragmatic reasoning.

► Little work has evaluated quantifier scope ambiguity in aphasic patients.
► Control subjects prefer certain quantifier scope interpretations.
► Semantic dementia patients exhibit good comprehension, but lose scope preferences.
► Advancing age is associated with similar loss of scope interpretation preference.