Conditioned Headturn Procedure

BITTSy can run conditioned headturn studies, a paradigm in which the child is trained (or conditioned) to turn a particular direction when they hear a particular event or a change in an event. Conditioned headturn can be used to test children's hearing (for audiometry - turn when a sound is heard), or can be used to test discrimination (turn when a change in a repeated sequence of sounds occurs). For the original use of this paradigm, see Eilers, Wilson & Moore, 1977; or see Kuhl , 1985 or Polka, Jusczyk & Rvachew, 1995, for methodological reviews.

In conditioned headturn studies, the child is seated on their parent's lap facing an assistant; the assistant maintains the infant's attention forward by playing silently with toys. Test trials consist of an auditory stimulus - either the presence of a sound, or a change in a background sound.

During training, the test trials are especially salient or obvious (a large change, or a loud sound). Immediately afterwards, a reinforcer then turns on to the side of the infant - originally, this was a lit-up animatronic toy, but it can be anything that would reward (and encourage) a child to look to that side. This reward plays briefly, and then turns off, so that the infant's gaze returns to the assistant, and the process repeats.

After a series of trials, the infant learns to expect that the reward will occur whenever the sound change happens. At this point, the reward itself is gradually delayed relative to the event, such that the infant begins to turn BEFORE the reward happens, or to anticipate it. This is the response that the experimenter is looking for - a turn towards the reinforcer when the particular sound occurs (before the reinforcer), rather than a turn in response to the reinforcer. There is a preset criterion for the test phase to end (e.g., three correct anticipatory head turns).

At this point, training ends, and the test phase begins; the experimenter indicates when a child is ready, and the computer randomly selects either a change trial (where the sound changes) or a control (no-change) trial, where the sound does not change. The experimenter indicates when the child turns his or her head; this leads to 4 potential trial results: a hit (the sound did change, and the infant turned appropriately), a miss (the sound changed but the infant did not turn), a false positive (the child turned even though there was no sound change), or a correct rejection (there was no change, and the child did not turn). These are then used to determine a child's discrimination ability. Only hits are reinforced during this test phase.

An alternative form of conditioned headturn uses two distinct reinforcers, and the infant is trained to turn either to the left or to the right. Other studies add a generalization phase after the standard test phase.

Creating conditioned headturn studies in BITTSy was made possible with the addition of the JUMP command in version 1.5. Due to its later introduction, implementing conditioned headturn paradigm is currently a bit "clunkier" than the other main paradigms BITTSy was designed to run, and the process of developing these protocols is typically more complex. While BITTSy can execute the typical trial and phase structures of conditioned headturn, there are some types of phase progression logic used in prior studies that are difficult to replicate exactly in BITTSy. However, similar to headturn preference procedure, the use of conditioned headturn has been limited by the unavailability of a standard system capable of running these procedures. The ability of BITTSy to run these paradigms provides an easy way for researchers to begin using this paradigm. We hope that BITTSy will allow more labs to adopt and adapt this paradigm for their research.