Infant Speech Lab


Babylab research methods and facilities 

infantgrootHead-Turn Preference

In this procedure babies are trained to make a head-turn towards a blinking light on their left or right side. The head-turn initiates the presentation of speech stimuli presented from a speaker behind the blinking light. The speech stops again when the baby looks away from the light for a couple of seconds. The length of the head-turn thus determines the length of the stimulus presentation. A stimulus that is in some way interesting to the baby will result in a longer head-turn than a stimulus that is less interesting. This interest, in turn, gives us information about types of linguistic knowledge that the baby has.

(Intermodal) Preferential Looking

infant2grootEye movements and looking times are an important source of information about the baby's knowledge. In the (I)PL paradigm, the eye movements of the baby are measured while the baby is looking at pictures of objects or a movie on a monitor. In language studies the baby listens to speech and is expected to make a link between the speech stimuli and the visual stimuli. The baby's face is video-taped and the eye-movements are analyzed later on in a program designed for this purpose. The looking times, and gaze-shifts of babies are indicative of their (linguistic) knowledge and expectations.

Tobii Eye-tracker

The Tobii T120x eyetracker is integrated in a monitor. With this device eye-movements are measured automatically while the baby participates in (intermodal) preferential looking studies (see above). During eye-tracking, infrared diodes – harmless to the eyes – are used. The reflections of the infrared light from the eye as well as the pupil position are measured. From this information the system software calculates the gaze position every 20 milliseconds. Pupil dilation is related to processing intensity, and can thus provide information about how hard a baby is thinking about a specific stimulus presentation.


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Near-Infrared Spectroscopy (NIRS) is a non-invasive brain imaging technique that is particularly suitable for infants because of ease of application and relative tolerance of movement. Neural activity is accompanied by changes in blood oxygenation, which can be detected by near infrared light. NIRS is an optical imaging technique that detects relatively slow changes in oxygenated (oxyHb) and deoxygenated (deoxyHb) hemoglobin concentrations related to neural activity. For taking the measurements, infants wear a cap much like an EEG cap, which can be equipped with several channels. A channel consists of a source-detector pair: each detector records the amount of light coming from a subset of neighboring sources. The baby is presented with visual and/or auditory stimuli, and the neural activity that results from processing these stimuli is measured. In our lab we use a NIRScout816 machine from the NIRx company.