A III-nitride semiconductor device which includes a charged floating gate electrode. While known programming is displayed on a television receiver, a plurality of sensors monitor the viewer or viewers for recognizable evidence of an emotional response that can be associated with a discrete program segment. The substrate has a weight per unit area of 150 to 350 gm2. Initially, purification procedures are described to reduce an initial blood sample to an analytical input to the instrument. The step of exploiting the sample includes comparing the value of an indicator of dispersion of the physical quantity, such as the variance of this quantity, to a predetermined threshold value. Additionally, the viewer’s eyes may be induced to follow a sequence of visual fixations at the same time as the passive viewer’s head is induced to execute attitudinal movements consistent therewith.