<P> In 1972 Sakitt conducted an experiment that combined elements of signal detection and threshold theory . Two key elements of the study were a high tolerance for false positives and a multiple - choice option on deciding whether or not a light was seen . In the classic studies described above, the tolerance for false positives was so low that threshold was biased upward . Based on statistical analysis of a large number of trials, 6 photons each absorbed by one rod near - simultaneously looked "very bright," 5 photons looked "bright," 4 photons "a moderate light," 3 photons "a dim light ." Two observers were able to see 2 photons as "slightly doubtful if a light was seen ." One observer saw a single photon as "very doubtful if a light was seen ." Zero photons were seen as "did not see anything ." </P> <P> The absolute threshold of hearing is the minimum sound level of a pure tone that an average ear with normal hearing can hear with no other sound present . The absolute threshold relates to the sound that can just be heard by the organism . The threshold of hearing is generally reported as the RMS sound pressure of 20 μPa (micropascals) = 2 × 10 pascal (Pa). It is approximately the quietest sound a young human with undamaged hearing can detect at 1,000 Hz . The threshold of hearing is frequency dependent and it has been shown that the ear's sensitivity is best at frequencies between 1 kHz and 5 kHz . </P> <P> The odor detection threshold is the lowest concentration of a certain odor compound that is perceivable by the human sense of smell . The thresholds of a chemical compound is determined in part by its shape, polarity, partial charges and molecular mass . The olfactory mechanisms responsible for a compound's different detection threshold is not well understood, as such, these thresholds cannot yet be accurately predicted . Rather, they must be measured through extensive tests using human subjects in laboratory settings . </P>

Who is known for their research on absolute threshold