The Rats and What They Proved

“Rat Park found something real in rats. It did not replicate reliably, and it proved less than Hari claimed.”

Bruce Alexander gave rats a choice between morphine solution and plain water. Rats kept alone in small cages drank more of the morphine solution than rats living together in a large colony he called Rat Park.

The original papers are real (Psychopharmacology, 1978 and 1979; Pharmacology Biochemistry and Behavior, 1981). In one phase of the 1979 study, isolated females drank about five times as much morphine as colony females, and isolated males about sixteen times as much as colony males.

What the experiments showed: in these rats, housing changed how much morphine they chose to drink. What they did not show: that social environment overrides pharmacological dependence in all circumstances. Later attempts gave mixed results. Bozarth, Murray and Wise (1989) found isolated and group-housed rats both learned to give themselves heroin. Petrie (1996) could not repeat the housing difference at all. A 2019 commentary by Gage and Sumnall in Addiction argued that the popular story has outrun the evidence.

Hari presented the results as though they settled the question of what addiction fundamentally is. They did not settle it. Environment is one important variable among several.

The rats in Rat Park still drank some morphine. They spent their lives mostly doing other things. That is the finding: mostly other things. Not no things.

Sources

• Hari, Chasing the Scream (2015)
• Gage & Sumnall, Addiction (2019)
• Alexander, Coambs & Hadaway, Psychopharmacology (1978)
• Hadaway et al., Psychopharmacology (1979)
• Alexander et al., Pharmacology Biochemistry and Behavior (1981)
• Bozarth, Murray & Wise, Pharmacology Biochemistry and Behavior (1989)
• Petrie, Psychological Reports (1996)