In the discussion following my post about the use bicycle helmets, many spoke about their own personal experiences with its use and how it influenced their decisions on whether to use them. An interesting side discussion then ensued about the use of anecdotal information in making decisions.
When it comes to making public policy, one clearly should not rely exclusively on anecdotes because those can be all over the place. One needs statistically significant patterns in the data before one makes up and enforces rules on the population at large. But anecdotes can be useful in that process in providing concrete examples of abstract ideas and it is also true that anecdotes are often the first indicators of whether there may be something worth investigating further. For example, clinicians often write up interesting cases for publication and these can turn out to provide important insights that lead to controlled studies.
On the other hand, when it comes to personal decisions about how to act, I think anecdotes can be very powerful determinants. We all make our own cost/benefit analyses, however informally, before we take any action and especially when the cost is very low, our estimate of the benefit can be hugely influenced by anecdotes.
In the case of helmets, the cost is low and having had an accident yourself or hearing of the death or brain injury of someone who did not have one can convince someone to wear one based on simple plausibility arguments, even if there are no studies showing benefits, and this is perfectly fine. (I don’t know if such studies exist or not. I am simply using this as an argument.) But when it comes to governments imposing mandatory helmet rules, then they need something more than anecdotes. They need real evidence of the safety and public health benefits.
When I am driving, I always insist that everyone wear seat belts, even if they are in the back seat, although the law does not rehire it. Why? I haven’t actually looked at studies on the safety of back seat passengers but the cost of doing so is so low, and the benefits so plausible, that it seems silly not to do so.
Incidentally, Baxter the Wonder Dog also always wears a seat belt. We put a special harness on him and the seat belt passes through the loop. This gives him some limited movement on the back seat that allows him to lie down but in the event of an accident he will not be flung and injured. Also I have read (anecdotes!) about how dogs allowed to move freely can distract the driver by sudden movement. The writer Stephen King, for example, was seriously injured when walking along a road when he was hit by a truck whose driver had an unbelted dog that suddenly moved onto his lap, causing him to swerve and hit King. I have no idea if there are studies that show that seat belts for dogs reduces their injuries in collisions or reduces driver distraction. But anecdotes and plausibility about the potential benefits were enough for me to decide.
And I don’t see any problem with that.