For a smart material to be able to send out a more complex signal it needs to be nonlinear. If you hit a tuning fork twice as hard it will ring twice as loud but still at the same frequency. That's a linear response. If you hit a person twice as hard they're unlikely just to shout twice as loud. That property lets you learn more about the person than the tuning fork.

Summary

The quote emphasizes the importance of nonlinearity in smart materials. It compares the behavior of a tuning fork, which responds linearly by producing a louder sound at the same frequency when struck harder, with that of a person who does not simply shout twice as loud when hit twice as hard. The nonlinearity demonstrated by the person allows for a deeper understanding of their characteristics compared to the predictable response of the tuning fork. This highlights the need for complexity and variability in materials to enable more sophisticated and informative signals or interactions.

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