Using Your Head: Measuring Infants' Rational Imitation of Actions

Recruit a number of 14-month-old infants. Participants should have no history of developmental disorders and have normal hearing and vision.

Because infants of this age can be uncooperative or fussy (e.g., refuse to watch a demonstration) and this experiment requires two sessions, expect to recruit and test extra participants in order to obtain sufficient data.

1. Data collection

1. Session one
   1. Place a touch-sensitive lamp (at least 6 in diameter) on a box or low platform, at a height where the experimenter can reach it with their forehead.
   2. Set up a rectangular table with two chairs on one side–one for the experimenter and one for the parent. Place the lamp out of sight but nearby, such as underneath the table.
   3. Sit in the chair on the right, invite the parent into the room, and have them sit in the chair to the left, approximately 8 in away, with the infant on their lap.
   4. Provide a few small toys, and allow the infant to play with them at the table for approximately 1-3 min. This helps the infant become comfortable with the environment.
   5. While the infant is playing, explain to the parent that the experimenter will be demonstrating an action for the infant, and the parent should remain quiet and avoid interacting with their child while the demonstration is taking place.
   6. Put away the toys, and place the touch lamp on the table.
   7. Begin the demonstration by getting the infant’s attention. At this point, participants are randomly assigned to one of two conditions, with an equal number of participants in each condition.
      1. Hands-occupied condition: The experimenter pretends to be cold by saying “Brrr.” They wrap a blanket around themselves, which they continue to hold with both hands.
      2. Hands-free condition: The experimenter pretends to be cold by saying “Brrr.” They wrap a blanket around themselves, and then rest both hands flat on the table in front of them.
   8. The experimenter leans forward and touches the lamp with their forehead and then straightens their back to return to an upright position. This action is repeated a total of three times over a 20-s period.
   9. If the infant becomes distracted during the demonstration, say the child’s name and “Look over here.” or “See what I have.” to gain the child’s attention. However, never use words such as “touch head” or “copy.”
   10. When the demonstration ends, escort the parent and infant from the room.
   11. Before departing, instruct the parents not to discuss the demonstration or model the action for their child.
2. Session two
   1. Participants return seven days after session one.
   2. Set up a video camera to record the participant’s torso, head, and the tabletop.
   3. Escort the parent and infant into the testing room, and have them sit at the table as during the first session.
   4. Provide toys for the child to play with for 1-3 min.
   5. Remove the toys, and place the touch lamp on the table directly in front of the infant. The touch lamp should be turned off, so it does not accidentally illuminate.
   6. Record the infant’s behavior for 20 s after they initially make contact with the touch lamp.
   7. End the session, and thank the parent and infant for participating.

2. Analysis

1. Two independent raters, who are blind to the participant’s condition, code video recordings of each participant.
2. The dependent variable is whether the participant leans down and touches the lamp with their head during the 20-s session.
3. Each coder provides a dichotomous yes/no response based on whether the participant engaged in the action.
   1. “Yes” means the infant used their head to make contact with the lamp, and “no” means they did not. For coding purposes, a “yes” response includes leaning toward the panel, straining to touch it with the head, but missing it by a few inches or less.
4. Compare each coder’s yes/no responses, and resolve any disagreements through review of the video and discussion.
5. Analyze whether the proportion of infants using their heads is different between the two conditions.