The p-value distribution of a set of heterogeneous results, as collected by Head et al., should be a mixture distribution of only the uniform p-value distribution under the null hypothesis $$H_0$$ and right-skew p-value distributions under the alternative hypothesis $$H_1$$. Questionable, p-hacking behaviors affect the p-value distribution. An example is optional stopping, which causes a bump of p-values just below .05 only if the null hypothesis is true (Lakens 2014).