Research ArticlePSYCHOLOGY

The origin of pointing: Evidence for the touch hypothesis

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Science Advances  10 Jul 2019:
Vol. 5, no. 7, eaav2558
DOI: 10.1126/sciadv.aav2558
  • Fig. 1 Reference-fixing experiment, setup.

    Superimposed on the left image, we see two lines, one in red and one in green. The arrow line (red) extends along the angle of the finger; the touch line (green) extends from the participant’s eye through the fingertip. Our prediction was that the green line would be a better predictor of what someone is pointing at than the red line. The image on the left illustrates the apparatus and setup for 3-year-olds to adults, the image on the right illustrates the setup for the 18-month-olds.

  • Fig. 2 Reference-fixing experiment, results.

    The location of the dots on the vertical axis shows the distance of either the touch line or arrow line in degrees from the target (target at 0°). Dots depict individual means, lines connect the arrow, and touch measures of individuals. Box around 18-month-olds indicates that a modified procedure was used.

  • Fig. 3 Rotation experiment, setup.

    On the left, the 2D condition, in which participants typically point with their hand flat; in the center, the participant rotates her wrist to the right to point at the right side of the box in the 3D condition; on the right, the participant rotates the wrist of her right hand to the left to point at the left side of the box.

  • Fig. 4 Rotation experiment, results.

    Likelihood of wrist rotation matching the side of target is depicted on the y axis. Dots depict individual averages, and connecting lines depict individual performance across conditions. Box around 18-month-olds indicates that a modified procedure was used.

  • Fig. 5 Interpretation experiment, main conditions.

    On the left is the arrow condition: Here, the vector extending through the angle of the pointing finger intersects with the same object the figure is gazing at (the yellow cup); on the right is the touch condition: Here, the object the figure is gazing at is the same one the fingertip is closest to touching (the red cup). The 18-month-olds and 3-year-olds reliably pick the red cup in the condition on the right but are at chance in deciding between the red and yellow cup in the condition on the left (Credits: authors; C. O’Madagain, Max Planck Institute for Evolutionary Anthropology).

  • Fig. 6 Interpretation experiment, results.

    Likelihood of choice matching gaze is depicted on the y axis. When participants follow the arrow, their choices match the gaze in the arrow condition; when participants follow the touch, their choice matches the gaze in the touch condition. Dots depict individual averages, and boxes depict sample means and SE. Box around 18-month-olds indicates that a modified procedure was used.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Interpretation experiment, controls.
    • Fig. S2. Interpretation experiment—results of control 2.
    • Details on Materials and Methods
    • References (1925)

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