Explanations are social, and when people try to explain something, they usually seek input from others. We present a simple theory of how people use the explanations they encounter as clues to the broader landscape of possible explanations, informing their decision to exploit what has been found or explore new possibilities. The challenge of coming up with novel explanations draws people to exploit or imitate appealing ones (information cascades); this draw increases as less appealing alternatives become more distant (the ``strawman'' effect). Conversely, pairs of low-quality explanations promote exploratory behavior or long-leaps away from observed attempts, and pairs of divergent high-quality explanations can lead to merging and syncretism. We use a transmission-chain experiment to test, and confirm, these predictions. Intriguingly, we also find that while people imitate good explanations, their imitations often fall short in quality. Our work provides new insight into how collective exploration can be promoted, or stalled, by implicit information about what is yet to be discovered.

Transfer of information between senders and receivers, of one kind or another, is essential to all life. David Lewis introduced a game theoretic model of the simplest case, where one sender and one receiver have pure common interest. How hard or easy is it for evolution to achieve information transfer in Lewis signaling?. The answers involve surprising subtleties. We discuss some if these in terms of evolutionary dynamics in both finite and infinite populations, with and without mutation.