By three weeks of age, the human neonate demonstrates behaviours which are quite different with an object and with a human interactant. He also demonstrates an expectancy for interaction with his caregiver which has clearly defined limits, as demonstrated behaviourally. In microanalysis of videotape, we saw regularly a set of interactive behaviours which were demonstrable in optimal face-to-face interaction between infants and their mothers. All parts of the infant's body move in smooth circular patterns as he attends to her. His face-to-face attention to her is rhythmic with approach-withdrawal cycling of extremities. The attention phase and build-up to her cues are followed by turning away and a recovery phase in a rhythm of attention-non-attention which seems to define a cyclical homeostatic curve of attention, averaging several cycles per minute. When she violates his expectancy for rhythmic interaction by presenting a still, unresponsive face to him, he becomes visibly concerned, his movements become jerky, he averts his face, then attempts to draw her into interaction. When repeated attempts fail, he finally withdraws into an attitude of helplessness, face averted, body curled up and motionless. If she returns to her usual interactive responses, he comes alive after an initial puzzled period, and returns to his rhythmic cyclical behaviour which has previously characterized their ongoing face-to-face interaction. This attentional cycling may be diagnostic of optimal mother-infant interactions and seems not to be present in more disturbed interactions.