Peter J. Lang conducted a series of experiments [P. Lang, 1988] using a database of photographs (IAPS) as the emotional stimulus. Slides of diverse content were collected into this study, 480 in all. The content ranged from sexually explicit material, to human injury and surgical slides, to pleasant images of children and wildlife.
For each slide a measure of valence and arousal was assessed and plotted in a two-dimensional space. The quantification of valence and arousal was conducted by subjects using a Self-assessment Manikin (SAM) [Lang and Bradley, 1994]. Each subject was asked to view the slide and mark down on paper their assessment of the valence and arousal. The mean response was plotted on the two axes, see figure 2-1. Over hundreds of subjects, this technique yielded a high correlation between subjects and a low standard of deviation.
[Figure 2-1: Lang used pictorial images to
represent the axis of valence and arousal to compensate for language
connotation confusion or misunderstanding.
]
After mapping out the valence-arousal space, Lang assigned emotionally descriptive labels, based on the content of the pictures, to several key areas of the space. The first quadrant contains the positive valence, high arousal stimuli that he called ``joyful'' or ``excited''. The second quadrant (low valence high arousal) included areas of ``hate'', ``enraged'', and ``fearful''.
This experiment has been verified numerous times. Three researchers in particular, Ward Winton, Lois Putnam and Robert Krauss, conducted a similar slide viewing self-assessment experiment [Ward Winton, Lois Putnam, and Robert Krauss, 1984] using sensors to monitor heart rate (HR) and skin conductance (SC). The introduction of these sensors provided a method for ascertaining the relationship between autonomic responses and the slide induced emotional experiences.