Costly Signals:

Wired:

"What makes signals work is that they cost something; you have to give up something. That’s what elevates talk from cheap to credible. Signals become meaningful only if they are costly."

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"Grafen illustrated that in costly signaling situations, the signals are clearly handicaps: They are more costly than not doing them. If the advertising was not costly, the signals would not function the way they do. All males voluntarily advertise more than they need (which is costly), higher quality males advertise more, and females use the advertising they perceive as a reliable guide to quality. Through this argument, Grafen came to the surprising conclusion that the cost of the signal is essential to its functioning: The signal is selected specifically because it is costly to the signalers and reduces their fitness in that area. Hopefully males are repaid for their costly signal by the interpretation of the signal by females. Grafen proves that handicaps are not just one possible kind of signal: He claimed that if we see a characteristic in an organism that signals its quality, it must be a handicap."