A great deal of my research over the years has fallen in to the area of Behavioural Pharmacology. That is, the study of physiological and behavioural mechanisms by which drugs operate, encompassing not only the effects of drugs on behavior but also how behavioural factors contribute to the actions of drugs. From the mid 1990's to 2000 my behavioural pharmacology work research focused on modelling the memory deficits observed in neurodegenerative disorders such as Alzheimer's Disease (e.g., Harper et al., 1994; Colombo et al., 1997; Harper et al., 1998). This research moved from the theoretical to a more applied focus as I examined pharmacological approaches to overcome memory deficits (e.g., Harper, 2000).

Between 2000 and 2015 my research moved to examining the comparative roles played by the brain neurochemical systems serotonin and dopamine in memory function. Consistent with my earlier work, this research was inspired by modelling a 'real-world' situation (in this case the neurochemical changes brought about by exposure to drugs of abuse such as amphetamine, cocaine, and ecstasy). The various research projects over this period incorporated work determining and modelling the exact cognitive mechanisms by which memory-task impairments arise (e.g., Harper et al., 2005, 2006; Kay et al., 2010, 2011) as well as including studies with potential applied value concerning pharmacological means to overcome memory dysfunction (e.g., Harper et al., 2006; Harper, 2011).

A key underlying theme underlying much of my research has been the employment of approaches from the Comparative Cognition area. That is, the study of cognitive processes (e.g. memory, decision making, time perception, attention, etc.) in non-human animals, the interplay between cognition and biology, and the comparison of cognitive function across species. In addition to providing the basic methodology of my Behavioural Pharmacology work, I have broadly used a comparative cognition approach to a wide range of topics over the years, including:
• Human memory,
• Time perception,
• Impulsivity,
• Visual attention,
• Road safety, &
• Animal welfare.