Place the camera centrally to the face of the participant. If using a computer to present stimuli, place it below the screen rather than above it, to gain effective facial expression coding.
Keep the scene behind the participant uncluttered to reduce interference with the facial analysis. Provide good, even lighting to ensure the features of the face are well-defined with no shadows.
It is really important that all of the participant’s face is seen by the video. Set up the ideal distance from chair to computer with one participant, ensuring their back is set back against the chair and mark this position, to ensure all further participants sit in the same place.
Good analysis is impacted by participants looking down at a keyboard. If key presses are involved then use keys that are easy to use, such as ‘F’ and ‘J’. Place stickers on these keys to make locating effortless. A familiarisation trial may be useful before the experiment.
Lab studies can result in facial expressions that may be less intense than real life. Creating engaging studies can help with this. A pilot trial can provide you with an insight into how effective the study is.