The Supreme Court accords starkly different treatment to private expression and government speech for First Amendment purposes. While regulation of private speech generally must be viewpoint neutral, the government is subject to no such requirement when it engages in speech of its own. But the line between private expression and government speech is often fuzzy. To draw this distinction, the Supreme Court has placed increasing emphasis on whether members of the public reasonably perceive the relevant expression to be private or government speech. We think this turn toward public perception is a welcome development: government intervention in the marketplace of ideas is especially dangerous when it is nontransparent, so before allowing government officials to escape the viewpoint-neutrality requirement, courts should verify that the public actually perceives the speech in question to emanate from the government. But the Court has so far failed to develop a reliable method for determining how ordinary citizens distinguish between private and government messages, relying instead on armchair speculation. Meanwhile, scholars have not yet mustered any evidence as to when and why individuals understand messages to be private expression or government speech.

To begin to fill this empirical void, we presented a variety of speech scenarios to a nationally representative sample of more than 1200 respondents and asked the respondents to assess whether the speech in question was the government’s. Some of the speculative claims made by the justices in recent government speech cases are borne out by our survey, but others prove less accurate. We further find that respondents are somewhat more likely to attribute messages to the government if they agree with those messages themselves; in this respect, lay people may be little different from judges, whose decisions in government speech cases sometimes seem to be influenced by ideology. We end by considering whether courts should consult survey evidence in resolving cases that involve government speech claims. An advantage of survey experiments is that they can be used to disentangle the effects of medium from the effects of message, reducing the risk that government speech doctrine will systematically favor some messages over others. To be sure, the use of survey evidence raises a number of implementation issues that require careful thought, but we ultimately conclude that an empirically informed government speech doctrine would protect First Amendment values more successfully than a doctrine dependent upon judicial guesswork.