Quote from Riskmanager:
Definitely a basic understanding of game theory.
When you're dealing with a single chart in a single time frame, technical analysis is enough. But if you're also watching the technical patterns in the time frames above your trading frame, understanding the strategic interdependencies can be the decisive factor for determining the probabilities of a collective behaviour pattern taking place.
Some key words to google for: "dominant strategy", "band wagon effect", "brinkmanship", "prisoner's dilemma", "evolutionary game theory", "lotka / volterra theorem", "tit for tat".