If you want to calculate how billiard balls move you have to include the gravity of the people in the room in your calculation from the 9th time the balls hit each other, Michael Berry explained in 1978. This is practically impossible, and that unpredictability makes billiards a game. In psychology, it is often practically impossible to measure all variables that affect people's behavior, for example because of that annoying human characteristic 'free will'. However, there are plenty of situations where we can make extremely good predictions.

For example, in 1935 Ridley Stroop asked one-hundred students to pronounce the colors of squares
(█ █ █ █), and to pronounce the color in which words were written (while the words have a different color-meaning: yellow green blue red). Although the meaning of the words is irrelevant to the color naming task, people cannot resist to process the meaning of the words, which makes them slower in the second task.

With one-hundred students, a piece of paper, and a watch, the observed difference was statistically more likely than the 5 sigma which the existence of the Higgs boson was recently demonstrated at CERN. Alphas and betas do not necessarily vary in the certainty with which they can make scientific statements. But where the factors that make people happier are just as difficult to predict as a game of billiards, we do not consider human happiness to be a game. And so it is up to psychologists to not only investigate how quickly people can name colors, but to also face the challenge to try to predict, at least to some extent, human behavior, despite its extreme variability.Brainmatters | Alphas and betas