I don’t need words to think about the shape of a car, or how to throw a football, or the taste of a chocolate chip cookie. In fact, things like that are probably easier to think about without using language. That’s why the strong form of the Sapir-Whorf hypothesis — that language is necessary for conscious thought — doesn’t hold up. But even if language isn’t required for some domains, it’s still possible that it is required for certain types of mental processes. It may even be required for some thoughts that aren’t obviously related to language.
Some research suggests that understanding the thoughts of others — having a theory of mind — is one such process. Many children who are late in learning language are also late in developing a theory of mind. This story illustrates the classic theory of mind test:
Mouse nibbles cheese.
Mouse puts cheese under box A
Mouse leaves room
Cat enters room, moves cheese from box A to box B, and leaves.
Where does Mouse think the cheese is?
Very young children will say box B, because that’s where the cheese is now. But at around age 4, they’ll correctly answer box A, since Mouse has no way of knowing that Cat moved the cheese. Older children have successfully developed an important aspect of theory of mind — they understand that Mouse falsely believes the cheese is in box A. But does understanding false beliefs of others require language?
Ashley Newton and Jill de Villiers developed a very clever experiment to test this question. They showed 66 adults two of four silent, language-free videos depicting scenes like the one I described above. While they watched the videos, some of the viewers also had to repeat a series of words spoken to them through headphones. Other viewers tapped out a musical rhythm while watching the videos. Half the videos showed false belief scenarios (where the mouse left the room while the cat moved the cheese), and half the videos should true belief scenarios (where the mouse watched the cat move the cheese). Then they were asked where the mouse thought the cheese was. Here are the results:
When the test was a true belief test, viewers were accurate, whether they were being distracted by the rhythm or the language activity. But viewers who watched the false-belief video while repeating words successfully completed the false-belief task less than half the time. People who repeated rhythms instead of words were nearly as accurate on the false belief task as they were on the true belief task — indeed, there was no significant difference in their performance on the two tests, and they were significantly more accurate than those distracted by the language task.
So repeating words disrupts the false-belief test, not the true-belief test, while repeating rhythm disrupts neither test. Newton and de Villiers say there are a number of aspects of language processing that could be responsible for interfering with the false-belief test, but it’s quite clear that some sort of language processing is necessary in order to reason about false beliefs. So while language isn’t a requirement for all thought, it most definitely appears to be a requirement for some thought.
Newton, A.M., Villiers, J.G. (2007). Thinking While Talking: Adults Fail Nonverbal False-Belief Reasoning. Psychological Science, 18(7), 574-579. DOI: 10.1111/j.1467-9280.2007.01942.x