In so-called Headturn Preference Paradigms (HPP), it is measured how long children keep their head turned to an auditory stimulus (e.g. a certain word or sentence) at the side. This allows to conclude how long the infant pays attention to the stimulus. This method can be applied to infants at the age of 4 to 24 months. It has been an established method for the last 20 years, and has been used all over the world to investigate language acquisition.
There is a chair in the cabine (see the photograph on the right) on which a parent sits with his/her child on the lap. The cabine only has three lights in it; a green one in the front and two red ones at the sides. There is a camera behind the hole above the green light at the front, which allows the experimenter in the next room to see where the child looks at.
An experiment consists of several trials, usually 16. At the beginning of a trial the green light is on to draw the child's attention to the front. Then one of the red lights will start to flash. As soon as the infant looks to the flashing side recorded syllables or whole phrases will be played via loudspeakers. From this time on, it will be measures how long the infant keeps looking at this red light. When the infant turns away for more than two seconds or the auditory stimulus has finished, the red light will go off and the next trial will start.