First published in 1982. This book contains the content of the Indiana Conference of 1974. This Conference has met for each of the last seven years. At one time it was known as the Midwestern Mathematical Psychology Meeting, but as interest drifted toward more experimental and theoretical, but less purely mathematical work, the title became the Indiana Theoretical and Cognitive Psychology Meetings. The contributors to this Conference were requested to emphasize the relatively broad theoretical significance of their work, to incorporate the work of others, and if they were willing, to speculate about future developments