Seeing things differently: The viewing time alternative to penile plethysmography

This paper describes the use of viewing time (VT), how long a subject looks at a probable sexual stimulus, as an alternative to penile plethysmography (PPG). We then trace the history of VT to assess sexual interest from 1942 to the present. The first computer-generated stimulus set for PPG was developed by Canadian researchers. This set was tested using VT by the second author and found valid. The unavailability of the set for further use resulted in the authors developing a new, computer-modified set with an alternate form version. This required the modification and compositing of images of real people. The proposed research using this set is described. To avoid using real photographic imagery in the future we propose use of specialized computer software that permits development of images from scratch. VT is a limited technology and we close with descriptions of new ways to assess sexual interest and behaviour using virtual reality and virtual environments.