Like a parent being pestered with endless questions from a young child, most people will now and again find themselves following an infinite chain of cause and effect when considering what led to some particular event. And while many factors can contribute to an event, we often single out only a few as its causes. So how do we decide?

That’s the topic of a recent paper by Tadeg Quillien, a doctoral student in the Department of Psychological and Brain Sciences. The study, published in the journal Cognition, outlines how a factor’s role in an event influences whether or not we consider it to be a cause of that event.

In his paper, Quillien constructs a mathematical model of causal judgement that reproduces people’s intuitions better than any previous model. And in addition to providing theoretical insights, understanding how we reason about causality has major implications for how we approach problems overall.

Intuitively speaking, the event that has the strongest role in determining an outcome is generally considered its cause. In fact, philosophers and psychologists have observed humans ranking the causes of an event in different studies. For instance, if a match is found at the scene of a forest fire, people usually say the match caused the blaze, even though the oxygen in the air was also necessary for the fire to start.