Thinking while talking: adults fail nonverbal false-belief reasoning.

This experiment tested the ability of 81 adult subjects to make a decision on a simple nonverbal false-belief reasoning task while concurrently either shadowing prerecorded spoken dialogue or tapping along with a rhythmic shadowing track. Our results showed that the verbal task, but not tapping, significantly disrupted false-belief reasoning, suggesting that language plays a key role in working theory of mind in adults, even when the false-belief reasoning is nonverbal.