 Solution

Naturalistic facial evidence supports biological and social regularities, but gives limited support to a universal one-to-one code for basic emotions. The relevant contrast is between describing a facial movement and inferring its cause. The same visible action can accompany an emotional episode, communicate affiliation or serve a task. A strong basic emotion theory needs independent evidence linking a category of felt emotion to a characteristic pattern across situations, rather than defining the category by the pattern it is supposed to explain.

Posed photographs are useful controlled stimuli, but agreement about them answers a different question from why people move their faces in ordinary life. Forced-choice emotion recognition supplies observers with labels and alternatives; it can encourage consensus even when spontaneous descriptions would differ. Recognition of a prototype also does not establish that its full configuration occurs frequently in lived episodes. Naturalistic studies should therefore code movements independently of a category judgment, record the social setting, and obtain an independent indicator of experience where possible. The Facial Action Coding System helps separate visible actions from their interpretation; anatomical coding is not itself a measurement of feeling.

Robert E. Kraut and colleagues' 1979 observations make the methodological issue concrete. At a bowling alley, bowlers were especially likely to smile while socially engaged, including when facing companions, rather than simply after a successful delivery. Observations in other settings also implicated social engagement. Bowling supplies identifiable outcome events and changes of orientation towards an audience, so it offers a useful setting for separating success from immediate social contact. However, a good score is an imperfect indicator of what that individual feels at that instant; the study cannot infer the absence of happiness merely from a lack of smiles.^[ref]

María-Ángeles Ruiz-Belda and colleagues addressed this limitation in 2003 by adding reports of feeling in field studies of bowlers and soccer fans. Among those reporting happiness, smiling was much more probable during social interaction than outside it. The key contribution is the separation of reported happiness from the presence of a smile, not merely the observation that social people smile. Reports still have timing and reconstruction limitations, and social interaction can itself alter felt intensity. Nevertheless, these observations are difficult to reconcile with the simple claim that happiness reliably releases a smile regardless of audience.^[ref]

The evidence does not require treating biological expression and communication as mutually exclusive. An inherited movement repertoire could become selectively deployed towards partners. Conversely, describing a smile as communicative does not show that its producer lacks happiness. A display rule may suppress or amplify a response. But if every absent expression is retrospectively called suppression and every unexpected expression is called a disguise, the claim loses predictive content. A useful version must specify the circumstances of suppression independently and predict differences before seeing the faces.

Evidence from blindness strengthens the case for a biological contribution without settling the strong universality claim. David Matsumoto and colleagues compared spontaneous expressions of congenitally blind, noncongenitally blind and sighted athletes. Similarities show that visual imitation is not necessary for all features of the observed repertoire. They do not remove social experience, other sensory learning, shared anatomy or competition-related goals. Nor do they establish a unique correspondence between each movement and a consciously felt category.^[ref]

A complementary result concerns interpretation rather than natural production. Rachael E. Jack and colleagues used generated dynamic faces and reverse correlation to estimate observers' category representations. Cultural differences in those representations challenge a single universal observer code. This is not direct evidence that the same cultural groups make different spontaneous movements in every emotional situation. Production and interpretation require separate tests.^[ref]

A decisive programme would sample episodes rather than only successful examples, include nonsocial and social periods within the same people, and obtain time-linked reports without prompting a fixed inventory of categories. Facial coders should be blind to reports and outcomes; analyses should distinguish within-person effects from differences between people. Researchers should test the entire distribution: how often a movement occurs without the proposed feeling, and how often the feeling occurs without the movement. A distinctive expression might still be informative without being necessary or sufficient. To establish a specifically basic category, the pattern must also outperform alternatives based on emotional valence, emotional arousal, action and social intention.