Knocking on wood may not be magical, but superstition proved helpful in understanding why the ritual was effective. Across cultures, superstitions intended to reverse bad luck, like throwing salt or spitting, often share a common ingredient. In one way or another, they involve an avoidant action, one that exerts force away from oneself, as if pushing something away.

This pushing action turns out to be important, because people’s beliefs are often influenced by bodily feelings and movements. For example, other research shows that people tend to agree with the same arguments more when they hear them while they are nodding their head up and down (as if they were saying “yes”) rather than shaking it from side to side (as if they were saying “no”).

Because people generally push bad things away, we suggest that they may have built up an association between pushing actions and avoiding harm or danger. This led us to speculate that when people knock on wood, or throw salt, or spit, the ritual may help calm the mind, because such avoidant actions lead people to simulate the feelings, thoughts and sensations they experience when they avoid something bad.