Original: Influenced by the ideas of William McDougall, Lorenz developed this into a "psychohydraulic" model of the motivation of behavior, which tended towards group selectionist ideas, which were influential in the 1960s.
Simplified: Building on the ideas of William McDougall, Lorenz developed this into a "psychohydraulic" explanation of the motivation of behavior, which tended towards group selectionist ideas, which were influential in the 1960s.