Rat Park was a study conducted in the 1970s by Bruce Alexander that challenged the dominant view that drugs cause addiction. In Rat Park, which was a more natural and enriched environment compared to standard lab cages, rats had much less appetite for morphine. When rats that had been forced to consume morphine were given a choice in Rat Park, they mostly chose plain water over morphine water. This supported Alexander's hypothesis that addiction is driven more by environmental factors like isolation rather than inherent properties of drugs. However, the Rat Park study was initially rejected by major journals and its funding withdrawn.