By examining the correlation between autonomic signals and self reported pleasantness, Winton, Putnam, and Krauss set out to discover the relationship of valence to the physiological responses of HR and SC. They selected five categories of emotionally evocative photographs to use as stimuli - Scenic, Erotic, Food, Unusual, and Morbid. Subjects viewed the slide and rated it; all the while their HR and SC were being recorded. The results from the Lang experiment validated the self reported responses Winton, Putnam, and Krauss collected.
By comparing the measured signals to the Lang category and self-reported ratings, Winton, Putnam and Krauss discovered that valence predicted HR response. The unpleasant categories were characterized by a significantly lower HR (in beats per minute) than other categories. The pleasant slides were succeeded by a marked increase in HR beats per minute, see figures 2-2 and 2-3.
[Figure 2-2: Second-by second changes in HR as a function of slide category.]
[Figure 2-3: HR change at post-slide 4 sec as a
function of self-reported slide pleasantness.]
From this experiment it was clear that by monitoring the HR of a subject viewing a slide, an observer could determine the valence of the stimulus. This is especially interesting since valence may differ from subject to subject for the same stimulus, yet the HR monitor could differentiate between a subject who was enjoying the experience and one who may have been thinking of something else or simply not liked the slide. There are many applications where assessment of an individual's valence might be useful, the most obvious being to supply the computer with this information so it can learn how to adapt its responses to better serve the user.
Putnam and Krauss also discovered the existence of a discrepancy between the physiological responses of men and women [Putnam and Krauss, 1991]. Where women have in general faster HR signals, men show a stronger SC response. This discrepancy has been verified in many subsequent experiments. The results of Dr. Manfred Clynes sentics experiments, using a different approach for monitoring and assessing subject's valence response, found characteristic signal patterns that did not differ between the sexes.