Data reduction and analysis
All data analyses were performed in MATLAB (MathWorks, Friedrichsdorf, Germany). Infants’
latencies of goal-directed eye movements in two areas of interest (AOIs) were analyzed. The first
AOI covered the position of the ‘‘giving’’ hand holding the ball (+ 1 visual degree in each direction).
The AOI around the action goal covered the area around the receiving hand (+ 1 visual degree in each
direction) [see Fig. 1A(I)].
We measured gaze shifts from the AOI around the giving hand to the goal AOI during the passing
action. Data were included in the analysis if infants fixated first on the AOI around the hand with
the ball and subsequently on the goal AOI (each for more than 200 ms) during a time period between
the end of the second ball squeezing and 1 s after the ball touched the receiving hand. The duration of
the reaching action, from the onset of the hand movement until the hand entered the goal AOI, lasted