Of the 480 pictures currently in the International Affective Picture
System (IAPS) only twenty-three were selected as representative of the
extremes of Lang's four emotional quadrants. Seven more were chosen
as neutral stimuli to pad the experiment and to provide contrast to
these extremes. Two different collections of pictures were compiled,
one for men and another for women.
Although a great deal of overlap exists, subject material was chosen
for equal opportunity as well as emotional index. Many photos of nude
women ranked highly in the men's subset. Therefore, despite their low
index, photos of nude males were included in the women's collection.