“The researchers made the discovery by studying three patients who were suffering from severe aphasia – they had lost the ability to understand, or produce, grammatically correct language.
For example, although they understood the words “lion”, “hunted” and “man”, they could not tell the difference between the sentences “The lion hunted the man” and “The man hunted the lion”.
But when they were presented with sums like 52 minus 11 and 11 minus 52, which were structured in a similar way, they had no problem. ”
The subjects could also still do arithmetic with expressions with parentheses.