One on one - with Paul Stern

One moment that changed the course of your career
When I completed my dissertation in 1975, I devoted the summer to thinking about my career direction. Would I continue to work in psychology, or throw all my graduate training aside and work on the environmental issues I had come to care more about? The moment came when rereading Garrett Hardin's famous article The Tragedy of the Commons. I realised that it presented a simple theoretical model of the human causes of environmental problems  that I could simulate in the laboratory. Others had noticed the same thing, but it was  a revelation to me. It led to my first publication, based on a small-group simulation of the choice of whether to join a carpool, which appeared in 1976. Although I ultimately decided that the simulation lacked external validity – it was far too easy to change the behaviour with simple interventions – I had discovered there were ways to do both environmental problems and psychology.

One person who inspired you
David Pimentel, an entomologist at Cornell University. In about 1974 I was very impressed with a paper he had published in Science analysing the energy inputs to grow an acre of corn, and how this had changed over time. I had become very concerned with the global environmental threats that were being highlighted by The Limits to Growth and other works, and I asked him if we could meet for lunch. He told me that he had submitted his paper against the objections of his colleagues in the agriculture school, who said it was totally outside his discipline. He was supposed to be studying insects' behaviour, not farmers'. He encouraged me to work on the problems I thought important and not to worry too much about disciplines.

One thing that you would change about psychologists working on environmental problems
The idea that the best way to work is to apply a psychological theory. Theory is really important, but if your work is problem-driven, you will often find that you need to modify theory, build new theory, or look for theory in unexpected places, rather than apply the theories that first come to mind. For example, early psychological work on energy conservation applied theories of attitude change and operant learning. This focused attention on frequently repeated individual behaviours that were easy to measure but that were not the major energy users. To address behaviours that matter more – travel mode choice, investments in home insulation, environmental activism, etc. – you need to look beyond psychology for useful theories. Often, by adding a psychologist's perspective to theories from elsewhere, you can develop fresh insights.

One challenge you think psychology faces
Being taken seriously by the environmental scientists and policy makers who really matter in shaping the human responses to environmental problems.

One problem that psychology should deal with
Improving human comprehension of climate change, which presents a difficult and perhaps unique cognitive challenge related to understanding risk. Climate change is discernible only when phenomena are aggregated across space and time, and the most important aspects are potential future events with uncertain probabilities. Therefore, personal experience and normal cognitive heuristics will mislead. Psychologists are best positioned to gain empirical understanding of how people think about climate change, what misapprehensions are likely to occur, and how to promote understandings that will support appropriate responses.