Letters Data, data everywhere

The John Henry effect

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f1804 (Published 02 April 2013) Cite this as: BMJ 2013;346:f1804
  1. Greg Irving, general practitioner1,
  2. John Holden, general practitioner2
  1. 1Department of Health Services Research, University of Liverpool, Liverpool L69 3GL, UK
  2. 2Garswood Surgery, St Helens, UK
  1. Greg.Irving{at}liverpool.ac.uk

The “Ballad of John Henry” tells of the legendary black American steel pin driver, John Henry, who swung a huge nine pound hammer driving railroad spikes on the Chesapeake and Ohio railway in the 1870s.1 John Henry was renowned for his strength among his fellow workers and could drive a steel pin into a track with a single blow instead of the usual three. The ballad centres on a competition between John and a mechanical steam powered drill, a controversial innovation that threatened to replace thousands of workers in a quest for greater efficiency. When John Henry heard that his fellow workers’ output was being compared with that of a steam drill, he challenged the railroad company to a contest, pitting his own skill and strength against that of the steam drill to see who could lay the track fastest.

The steam drill was positioned on one side of the track and John Henry on the other. When the signal to start was given, 2000 people came to watch the event. John Henry made more progress in a shorter time than the steam drill, and when he reached the finish line the steam drill was nowhere in sight. He won the contest but worked so hard to outperform the machine he collapsed and died in the process. This story is just one example of reactivity, the phenomenon whereby people alter their performance or behaviour when they are being observed. The term John Henry effect, also known as compensatory rivalry, was first suggested by Robert Heinich in 1970 then further developed by Gary Saretsky in 1972 to describe this behaviour.2

If we were to cast this tale into the future, then computers powered by big data would be represented by the steam drill and the doctor by John Henry.3 Perceiving the consequences of such an innovation as threatening to their jobs, status, or traditional patterns of working, doctors may go to extraordinary lengths to outperform the opposition. However, the increased work needed for victory may prove unsustainable for some and come at considerable personal cost.

Such effects may confound evaluation outcomes unless controlled for by robust experimental design—for example, adequate blinding. When such evaluations ultimately take place (and they will), we should not forget that doctors do far more than just crunch data (or lay track). Indeed, the interpersonal warmth, trust, and informality that characterise most clinical consultations is where we witness the real victory of human dignity, intuition, and lateral thinking over the politically driven degradations of the machine age.4


Cite this as: BMJ 2013;346:f1804


  • Competing interests: None declared.


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