Risk Homeostasis and Soccer Headgear

Do athletes take more risks when you give them better safety gear? That idea pops up in a NY Times piece today on the merits (or dangers) of soccer protective headgear. Apparently there is a major push underway in soccer circles for more players to wear a kind of padded headband. 

But not everyone agrees:

Players might develop a false sense of security, relying on headgear instead of proper medical evaluation after suffering a concussion, federation doctors say. Or, they say, players might feel invincible in headgear and play with reckless aggressiveness, displaying behavior known as the Superman effect.

This last sentence is essentially a restatement of a theory popularized by Canadian psychologist Gerald Wilde. He has argued for more than two decades that accident or injury rates remain relatively constant regardless of interventions intended to make a system safer. In other words, safer cars and better highways (and, presumably, protective soccer headgear) all lead people to collectively change their behavior such that the rate of risk remains constant.

Academics call the idea “risk homeostasis” and it is controversial. While some people like to present it as accepted wisdom, nothing could be further from the truth. Supporters of risk homeostasis’s tenets have been accused of selective empiricism, as well as being called flat-earthers and believers in phlogiston. Supporters say that critics are resorting to name-calling and strong-arm tactics.

Sadly for Wilde, while his argument has some appeal — people do adjust their behavior based on an action’s risk — the critics have the stronger case. Consider, for example, that while Wilde has made much of the idea that risk homeostasis is best supported by automative safety statistics, Brian O’Neill fairly convincingly dismissed it in a 1998 paper in Injury Prevention:

“… the motor vehicle crash death rate per capita in the United States dropped 26% between 1966 and 1987, and has dropped another 18% since then. I wonder how Wilde explains that?”

It seems likely, as O’Neill implies, that Wilde found a data set, then created an explanatory theory, but now refuses to abandon his theory when confronted with out-of-sample data.

None of this, of course, makes it into the NY Times, piece this weekend. Instead, we have risk homeostasis — the “Superman effect”, as the Times provocatively calls it — presented as some sort of common wisdom. It isn’t, and the Times should know better.


  1. Dr. Gerald Wilde says:

    It is with interest that I read your web page on protective gear for soccer players (I was one myself until the age of 14 or so). Before you make up your mind on “risk homeostasis theory”, may I suggest you consult my latest book (in English, “Target Risk” (published in 2001 by PDE Publications in Toronto; pde@drivers.com; first edition (1994) on the web: psyc.queensu.ca/target). You might be surprised by the large amount of empirical evidence in support of this point of view.There will be more such evidence in the 3rd edition. Sincerely, Gerald J.S. Wilde, Professor emeritus of psychology at Queen’s University, Kingston, Ontario, Canada

  2. James Hammett says:

    I notice that you cite the “Death Rate” from auto accidents, not the raw number of accidents.
    So even though the ‘accident rate’ may be the same, with a Modern Car the chance of death is going to be less. (In terms of the cost of the body shop and repairs, with the same number of auto accidents, it will be the same or higher (since alot of the safety of the passenger is paid for by the destruction of the car)