The attachment of the infant to the mother can be seen in open parkland when an infant is set free for exercise and play. In an area of safe space, a mother has little cause to restrain her child, nor, owing to other attractions around, to entertain or otherwise divert him. In order to deduce which of the women and infants make up kinship pairs, the observer postulates criteria for recognizing a pair; attachment is then conceived of as factors which identify a mother and her infant in field conditions.

The infant detaches himself from his mother but he maintains proximity to her, particularly around the age of 2 years, when his proximity- and contact-seeking are at their height. Yet, at this age, the infant shows most alertness to remote events. From 2 years old onwards, the presence of age-mates competes for the infant's proximity. Hence, the statistical data presented below is from observations which were made when the likelihood of interruption by neighbouring people was minimal.

Proximity to the mother can be defined as the child's being at rest beside her, or as his playing in her vicinity, or as a pattern of exploratory locomotion with the mother the centre of the territory he covers. In each of these aspects, the behaviour of 1-, 2- and 3-year-olds is distinguished by typical distances from the mother.

The infant's responsiveness to unexpected sights or sounds is inferred from the orientation responses he makes to them. In his postures and the distances he takes up from the mother, his feeling-states of alertness, fear, anger, uncertainty, fatigue and conflict are expressed; when thus activated, he tends to relate himself to his mother.