The numbers in parentheses are attempts to quantify the values of different outcomes. Thibaut and Kelley let a single number represent the rewards minus the costs of a given course of action. For example, Smith might mentally sum up the benefits of a life sentence as a + 14. He’d have the relief of escaping execution, a chance for human contact, plenty of time to watch TV, and perhaps a shot at parole later on. Of course the downside of a life term in jail would cancel out most of those benefits. Smith’s costs, which he might mentally rate as a - 11, would include permanent loss of freedom, guards’ continually telling him what to do, boredom, and fear of violence from other prisoners. Since the outcome of an interaction equals rewards (+ 14) minus costs (- 11), Smith would regard the consequence of a mutual confession as a bleak +3.