Development based on mutual action observation between parent and child

How would infants and toddlers catch the rhythm, and synchronize the timing to produce their body movements in the context of physical interaction with other persons? In order to approach this problem, we focused the behavioral characteristics of children’s rhythmic movement playing, and investigated the rhythm control and timing synchronization during “pat-a-cake” playing and/or dancing to movies by children.

The results were as follows: (1) In about 11 months old, infants responded to the children’s movies by some kinds of rhythmic full body movements, with the obviously different forms of movement; (2) In about 16 months old, infants manipulated the timing of response in synchronization with vocal priming, to initiate the full body movements as jumping, walking, and stretching, or bimanual movements as clapping or waving hands; and (3) Over 22 months old, they manipulated the forms of movement as well as the timing to synchronize with body movements of the models. They also showed an anticipation of the sequence, such as producing ahead the movement at some positions later in the sequence.

 

Stable frequency of preferred rhythm in spontaneous movements in infancy

Especially for the rhythmic movements by infants under 11-month, such as monotonically repetitive arm banging and full body swinging, we measured the frequency of repetition. They responded with the arm banging in 1.58 Hz, and the full body swinging in 2.13 Hz. McAuley and colleagues measured longitudinally the spontaneous motor tempo, through the unpaced tapping continuation task with preferred tempo. Their results showed that the frequency of tapping converged to approximately 2 Hz in childhood, and maintain it till the later period of adulthood (McAuley et al., 2006, in J. Exp. Psychol.: General, 135(3): 348-367). These suggested that monotonic repetition of spontaneous movement would follow the stable frequency of 2 Hz, in regardless of the body parts to be moved, and that this frequency would work even at the spontaneous rhythmic body movement in the early period of development.

These results are summarized into Table 1 as the behavioral development of temporal control in motor production.

 

Table 1  Behavioral development of temporal control in motor production in infancy

Table 1 Behavioral development of temporal control in motor production in infancy

 

Synchronization of two persons’ movements by implicit entrainment of motor rhythms

In the context of physical interaction with other person, the movements to be reacted vary spatially with the complex forms as well as temporally with specific rhythms and timings to the person. How would children manipulate their rhythm and timing of movement to synchronize other person’s movements which might have different rhythms and timings? To consider this issue, we conducted motion analysis into the “pat-a-cake” play by children and parents and examined the synchrony of children’s movement rhythm and timing of initiation with other’s movements.

We measured two temporal characteristics in each phrase of the pat-a-cake song: time delay of child’s movement initiation from the parent’s, and the duration of movement. From start to finish of the song, parent performed the movement sequence by the frequency of 2 Hz. Child, on the other hand, responded variously both in time delay and duration of movement. However, in the latter part of the song, child’s duration of movements was almost the same as parent’s ones. In addition, there’s almost no difference between child’s and parent’s initiation of movements. Therefore, child achieved synchronized performance of a complex movement sequence with her parent’s movement. Furthermore, in parent’s movements, the duration elongated moderately and the rhythm of movement got slightly slower through the course of the song.

These results showed the synchrony of parent-child pat-a-cake movements would be achieved by the child’s temporal manipulation of movements as well as the entrainment of parent’s rhythm and timings into child’s rhythm and timings, resulted in synchrony by a newly attracted rhythm for both persons.