There is a significant body of literature stating that caffeine is the most widely consumed drug in the world, yet its effects on operant behavior are little understood. Some of the current research on caffeine suggests that it may play a role in altering motivational states related to transitions between previous and upcoming work requirements. The purpose of the current study was to examine the effects of caffeine on postreinforcement pausing during transitions between small and large fixed ratio rudiments. Eight rats were exposed to five doses of caffeine and and a two-component multiple schedule. We found that caffeine does systematically alter the length of pausing during transitions between fixed ratio requirements, however the magnitude of the effect may be dependent on the baseline rate of responding.

This study was directed toward investigating effects of menstrual cycle stages and caffein ingestion on various physiological and psychological processes. Subjects maintained a daily log of basal waking temperature (BWT), occurrence of menstruation, and consumption of caffein containing beverages and medications. At each session, visuo-spatial discrimination, depth perception, and time estimation (15 and 30 sec) were assessed. The Menstrual Distress Questionnaire (MDQ), The Measurement of Depression (MOD), and a self-report scale were completed.Multiple linear discriminant analyses were conducted on menstrual cycle and caffein ingestion data. Variables that contributed significantly to the discrimination of level of caffein ingestion were visuo-spatial discrimination; MDQ Water Retention and Control; cervical, lumbar, and saccral temperatures; time required to reach baseline; and total daily consumption of caffein-containing beverages.