Correlation between dichotomous and continuous variables

I'm using the operator "Correlation Matrix" on rapidminer, which I believe uses Pearson Correlation, and the operator is able to calculate correlations for every  variable type, including binominals (dichotomous) and polinominals. 

I would like to know: how exactly is the operator calculating the correlation for example between a binominal and a numerical attribute? Wouldn't a pearson correlation only allow numerical variables? Does it simply convert binominals to 0 and 1, or is it  doing something else?

Thanks in advance,
Filipe G.B.