Headturn Preference Procedure (HPP)

The Headturn Preference Paradigm (HPP) measures the duration of an infant's headturn towards an auditorily presented stimulus. This gives us information about how long the infant is interested in a specific word or sentence. This method works with children between 4 and 24 months of age.

What follows is a description of the procedure. The child sits on the lap of a care-giver in a booth (see picture below).

Testing booth of the headturn lab

The booth is covered with white cloth and only contains three lights: a green one in the front and two red ones at the sides. Above the green lamp is a hole through which a camera is filming the scene that is transmitted to an adjacent control room. There, the experimenter is coding where the infant is looking.

An experiment contains multiple trials, 16 in most of our studies. At the beginning of one trial the green light in front is flashing to attract the attention of the infant. If she is looking the green light is turned off and one of the red side lights starts to flash. As soon as the infant is looking there the auditory presentation starts from a speaker behind the light. From this moment on the looking duration is measured. If the infants looks away for more than 2 seconds or the sound file presentation is complete the light is turned off and the next trial begins.

Some studies include a famliarization phase prior to the actual testing phase. During the familiarization the infant is presented with words or texts that are repeated for a fixed amount of time, e.g. one or two minutes. This allows us to contrast novel and familiar stimuli in the test phase and we can investigate whether infants look longer to new or old stimuli, which would indicate that they discriminate between both.

During the entire measurement the care-giver listenes to music over head-phones and thus is blind to the tested conditions. The experimenter is also blind to the conditions because the sound is turned off in the control room.

Most studies contrast two conditions, e.g. a familiar and a novel word or a grammatical and an ungrammatical sentence. If infants' looking times differ between the conditions, this is a consequence of their ability to discriminate between them and can not be explained by the lights because they are the same in both conditions. Also, both conditions are presented on both sides in order to avoid side biases affecting the results. Only the presentation of many trials and testing of lots of infants ensures that the results are not dependent on coincidence. That is the reason that we are unable to tell for one infant if she is able to distinguish between two conditions.

This method has been used now for over 20 years and it is valuable tool for language acquisition research all over the world.

http://www.uni-potsdam.de/en/babylab/information-for-parents/methods/language-acquisition.html