A parent's blank stare can unravel a baby in under two minutes
In Edward Tronick's Still Face Paradigm, a mother plays normally with her infant, then suddenly holds a silent, expressionless face for a few minutes. The baby tries everything — smiling, pointing, shrieking — to restart the exchange, then collapses into gaze-aversion and distress. First shown in 1975, it's become one of the most replicated results in developmental psychology.