The following samples demonstrate how to execute a secondary task or probe task while a subject completes another task in MediaLab. Visual, auditory and TTL signal probes can be launched at any time from your questionnaire. You can create a schedule of probes at either random or fixed intervals and get subjects' response times to the probes. The probes can span multiple items as the probe function runs independently of the experiment once launched. Response times are assessed using DirectX so their accuracy is very good.