A data processing device controls the image-recording device to capture a video, turn the video into a time series of luminance values, and analyzes the frequency spectrum of this time series. The device determines whether said series of images depicts a test subject. The device extrapolates the emotional response of a detected test subject to choices displayed on the display device during a time period encompassed by said series of images. The extrapolation of the emotional response measures the subjects time between heart rate events, the associated frequency spectrum, and where said captured video comprises a close-up depiction of a region of the subjects exposed skin.
