Visual Fixation Procedure (VFP)

Visual fixation is a type of habituation paradigm frequently used to study either infant auditory or visual discrimination. The Switch paradigm (Stager & Werker, 1997) is one type of visual fixation procedure.

In visual fixation, the infant is facing a central video screen which shows an image on each trial; at the same time, a sound is played. The infant's interest in the auditory stimulus is measured by how long they choose to look at the co-occuring visual image.

In most cases, the image is not intended to represent the sound; for example, the child might see a bullseye image, or a checkerboard, paired with a repeating sound (such as a syllable). At first, the image and sound are novel, so the infant attends for a fair amount of time. But as the trial repeats over and over, the combination of sound plus image eventually become less interesting, and the child's attention level drops. This is referred to as habituation; it is usually defined experimentally in terms of a set decrease in attention (e.g., looking 50% of the time as at the start of the study).

In BITTSy, the habituation criteria can be based on a percentage decrease from initial looking (e.g., the first 3 trials), or from peak looking (the 3 trials with longest average looking). You can also set the amount of decrease in looking (e.g., 50%, 60%) and the number of trials over which looking is averaged.

The Switch paradigm is a form of VFP in which infants are first "taught" one or two new words and then tested on their learning of that pairing. During the habituation phase, they are presented with a particular combination of auditory word and visual image. After habituation, the child is then presented with either the same pairing, or a "switch". For example, if the child was habituated with object A + sound 1 and object B + sound 2, they would be tested with either a correct pairing (object A + sound 1) or a switch (ojbect B + sound 1). If children have learned the specific pairing, they should dishabituate (or increase their looking) to the novel pairing.

See the habituation section for more information about setting up visual fixation/habituation studies in BITTSy.

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