Democracy, Mencken says here every day, is “the art of running the circus from the monkey cage.” But that’s not the way most political scientists see it. The leading theoretical paradigm in the field portrays political behavior as reflecting “rational choice.”

We love books with titles like “The Reasoning Voter,” “Reasoning and Choice,” and “The Rational Public.” Much of our thinking about democratic ideals and democratic reform is likewise built upon the self-congratulatory Enlightenment view of human beings as fundamentally rational, inclined (at least under the right conditions) to weigh arguments on their merits and arrive at empirically and normatively sensible conclusions. It is a very comforting assumption, which goes a long way toward accounting for its popularity despite much uncongenial experience. Once in a while, though, someone flashes a fleeting light on what’s really going on inside the monkey cage, and the results can be pretty scary.

Milton Lodge and Charles Taber’s 2013 book, “The Rationalizing Voter,” provides some remarkable examples of the gulf between Enlightenment ideals and real political psychology. Among the most remarkable are two studies conducted by their student Cengiz Erisen, who set out to study the impact on political thinking of “irrelevant stimuli.” These modest experiments seem to me to go a long way toward undermining the way we like to think about democratic citizens.

In one experiment, 224 subjects read and responded to policy statements regarding illegal immigration and energy security. For example, they might be asked to respond to the statement: “The number of illegal immigrants coming to the United States will drastically increase in six years.” Independent coders rated each response as a positive or negative thought.

Not surprisingly, subjects’ responses to the policy prompts tended to reflect their preexisting views about each issue. For example, pro-immigration subjects offered 34% fewer negative thoughts and 38% more positive thoughts than those who opposed immigration. However, that difference was dwarfed by the difference between subjects with similar views exposed to different “irrelevant stimuli.” Erisen’s data indicate that subjects exposed to positive stimuli offered 42% fewer negative thoughts and 160% more positive thoughts about illegal immigration than those exposed to negative stimuli.

What were these powerful “irrelevant stimuli” outweighing the impact of subjects’ prior policy views? Before seeing each policy statement, each subject was subliminally exposed (for 39 milliseconds—well below the threshold of conscious awareness) to one of three images: a smiling cartoon face, a frowning cartoon face, or a neutral cartoon face. According to Lodge and Taber, “Fleeting images of cartoon smiley faces have a larger effect than prior immigration attitudes on the valence of thoughts in response to illegal immigration policy prompts.”

In a second experiment, 125 subjects read and responded to six policy statements regarding illegal immigration (three pro- and three anti-, presented in random order). Again, the subliminal cartoon faces substantially altered their assessments of the policy statements — and the resulting negative and positive thoughts produced substantial changes in policy attitudes measured up to 45 minutes after the original presentation of pro- and anti- statements. According to Lodge and Taber, “Negative thoughts about a policy, whether they come from intrinsic political attitudes or incidental affective primes, reduce support for that policy, while positive thoughts increase support.”

Optimists may feel reassured by the fact that real political debates do not turn on subliminal cartoon faces. But Lodge and Taber point out that Erisen’s experimental results “bring us a step closer to understanding such real world phenomena as place-of-voting and ballot order effects, candidate appearance and trait attributions, the impact of symbols or emotive music in campaign advertising, the shadow of race or gender on political action, and motivated bias in counterarguing uncomfortable arguments or evidence.”

More important than these practical considerations, in my view, are the implications of Erisen’s findings—and of Lodge and Taber’s many other examples of “unconscious thinking and its influence on political attitudes and behavior”—for our basic understanding of democratic citizens. What sort of political science, and what sort of democratic theory, would make sense in a world where citizens’ responses to political arguments are powerfully shaped by subliminal smiley faces? What seems to be called for is a radical departure from our comforting Enlightenment faith in human reason, and from its contemporary manifestation in rational choice theory. I don’t know what that will look like; but it will not be nearly as smiley as what we have now.