The findings of continuous systematic observations on 4 newborn infants were reported, with emphasis on motor patterns in sleep, on reactions to external stimulation, and on responses to need tension.
A tentative explanation was presented that sought to relate the observed types of behavior to one another in terms of energy and threshold concepts. The various behavior forms were classified according to their sources and according to their presumptive connections with functions of the more fully differentiated personality:
1. Motor activity initiated by neural excitation, that is, by spontaneous activity of the central nervous system. To this category seem to belong startles and possibly other motor activity in sleep but none of the other observed behaviors.
2. Diffuse motor activity initiated by need tension or external stimuli, from which the later “acquired” behavior forms will differentiate. To this category would belong most of the motor activity during waking and possibly that during irregular sleep, but not, for example, the various kinds of mouthing or the pursuit movements.
3. Reflexly organized executive functions initiated by need tension such as hunger. Rooting and nutritive sucking would belong to this group and perhaps some of the hand sucking and mouthing before meals, but not crying or pursuit movements.
4. Need-"motivated" expressive movements which are reflexly organized precursors of affect expression. These would include crying and probably the smile and pre-cry face, but not spontaneous startle or sucking.
5. Practice behaviors (in Piaget's sense) that are at first reflexly organized and become stabilized through repetition. Once stabilized, they may be utilized either as need executive or as “voluntary” adaptive functions; they probably include hand sucking and mouthing after meals, but not startles or diffuse movements in sleep.*
6. Voluntary activities, which are at first reflexly organized, and elicited by external stimuli and which later become intentional. The visual and auditory pursuit movements and possibly the arrest of activity upon stimulation may be the first reflex predecessors of voluntary activity, whereas hunger crying probably is not.
Although motor behavior in the neonatal period is justifiably considered undifferentiated, it may be concluded from this study that differentiated reflex predecessors of several behavior forms are already distinguishable in the first few days after birth.