Holland, J. G. Human vigilance. Science, 1958, 128, 61-67.
2.
Hutt, C./Ounsted, C.The biological significance of gaze aversion with particular reference to the syndrome of infantile autism. Behavioural Science, 1966, 11, 346-356.
3.
Wyckoff, L. B. The role of observing responses in discrimination learning. PartI. Psychological Review, 1952, 50, 431-442.