Trump's tariff tactics follow a psychological playbook

From zero-sum thinking to loss aversion, the U.S. president's trade moves follow a psychological playbook Much has been written, spoken and thought about U.S. President Donald Trump's approach to trade with our country—specifically, what the hell to make of it. Prime Minister Mark Carney may look cool and collected, but more and more I wouldn't want to be drywall near his fist. Guesswork galore about trade discussions is the best any of us can do as the Aug. 1 deadline nears—if indeed any deal itself will be reached by that deadline. But Trump's tactics are hardly novel. They are slices…