This thesis assesses the link between action and cognition early in development. Thus the notion of an embodied cognition is investigated by tying together two levels of action control in the context of reaching in infancy: prospective motor control and executive functions. The ability to plan our actions is the inevitable foundation of reaching our goals. Thus actions can be stratified on different levels of control. There is the relatively low level of prospective motor control and the comparatively high level of cognitive control. Prospective motor control is concerned with goal-directed actions on the level of single movements and movement combinations of our body and ensures purposeful, coordinated movements, such as reaching for a cup of coffee. Cognitive control, in the context of this thesis more precisely referred to as executive functions, deals with goal-directed actions on the level of whole actions and action combinations and facilitates directedness towards mid- and long-term goals, such as finishing a doctoral thesis. Whereas prospective motor control and executive functions are well studied in adulthood, the early development of both is not sufficiently understood. This thesis comprises three empirical motion-tracking studies that shed light on prospective motor control and executive functions in infancy. Study I investigated the prospective motor control of current actions by having 14-month-olds lift objects of varying weights. In doing so, multi-cue integration was addressed by comparing the use of visual and non-visual information to non-visual information only. Study II examined the prospective motor control of future actions in action sequences by investigating reach-to-place actions in 14-month-olds. Thus the extent to which Fitts’ law can explain movement duration in infancy was addressed. Study III lifted prospective motor control to a higher that is cognitive level, by investigating it relative to executive functions in 18-months-olds. Main results were that 14-month-olds are able to prospectively control their manual actions based on object weight. In this action planning process, infants use different sources of information. Beyond this ability to prospectively control their current action, 14-month-olds also take future actions into account and plan their actions based on the difficulty of the subsequent action in action sequences. In 18-month-olds, prospective motor control in manual actions, such as reaching, is related to early executive functions, as demonstrated for behavioral prohibition and working memory. These findings are consistent with the idea that executive functions derive from prospective motor control. I suggest that executive functions could be grounded in the development of motor control. In other words, early executive functions should be seen as embodied.

Of all motor skills, manual reaching might be the one ability that matters most for infants’ perceptual, cognitive and social development. Reaching allows infants to learn about object properties, but also gives opportunities for socializing with others. The general aim of the present thesis was to study the importance of manual motor development in infancy from different perspectives; first, through examining stereopsis as a prerequisite for efficient reaching development, second, with regard to understanding others goal-directed reach actions by means of the mirror neuron system (MNS), and third, in relation to possible atypical development, with a specific focus on autism spectrum disorder (ASD). Study I shows that under monocular viewing conditions, infants at six, eight and 10 months of age perform slower and less accurate reaches. Longer times to object contact during monocular trials specifically imply that motor prediction is less effective when depth and distance information is compromised. Study II demonstrates that, by eight months of age, infants seem to have a MNS that functions in a similar manner to the adult MNS, thus activity can be registered over the motor cortex when infants simply observe an action they can master themselves. This activation is predictive, indicating anticipation of the goal of the observed reach. Study III indicates that infants at elevated familial risk for ASD present with reduced prospective motor control at 10 months of age. Compared to a low-risk control sample, high-risk infants perform reactive rather than predictive reach actions. Follow-up assessment at 36 months will show whether this measure can be used as a predictive diagnostic marker for ASD. The main contribution given by this work is the insight that it is important to take manual motor aspects into account when considering typical as well as atypical cognitive and social development, and in addition, that motor prediction is a key factor behind being able to timely execute and understand reaching actions.