When the Edge of Certainty is Close Enough

Compelling evidence of a causal link between food coloring and the aggravation of attention deficit hyperactivity disorder in certain children has prompted a UK behavioral psychologist to invoke "the precautionary principle” and call for a ban.

Jim Stevenson, professor emeritus in Southampton University's Brain Behaviour Laboratory, likens the state of knowledge of the effects of E-number coloring to what was known about lead and children’s IQ in the 1980s.

In that case, a sequence of statistical adjustments to take into account "confounding social differences" reduced the effect size to 0.17 – a figure "at the margins of certainty".

Sir Michael Rutter announced in 1983: “A marked reduction in the level of environmental lead is likely to make an important difference to some children. Moreover it is important to recognize that a small change in mean IQ or average behavior of the population as a whole will have a much greater effect at the extremes of the distribution […]. Accordingly, actions to cut down the amount of lead pollution of the environment should be worthwhile; there is sufficient justification for action now”.

Action duly followed, Stevenson writes, and it turned out to be a prudent use of the precautionary principle. The current evidence on food colors was comparable and the effect size data similar, but hedged health warnings were the extent of the response.

He reviews the argument in the latest edition of the Journal of Children's Services.

Read more online at: http://preventionaction.org/research/when-edge-certainty-close-enough/5144