Sometime you read a paper and you keep thinking about it. That’s what happened to me with the latest work from Xin Jin’s lab (yes, I am in awe of this work) in which they show that there exists a hierarchical organization of learned action sequences . First of all, what’s an action sequence and what’s the problem? Let’s assume I need to do ABCD to obtain a given reward (i.e. [toss the ball (A)], [bring the racket shoulder height (B)], [extend the arm(C)], [hit the ball(D)] ->