I came across a new word the other day in the course of my work – “Hysteresis”. Hysteresis is defined broadly as the tendency to repeat a previous action just undertaken, or more officially as ‘the lagging of an effect behind its cause; especially the phenomenon in which the magnetic induction of a ferromagnetic material lags behind the changing magnetic field’. I wonder if hysteresis accounts to some extent for the phenomenon by which, when you get off a bicycle after riding for a while, your legs feel as if they are still pedalling, or when writing your Christmas cards in a repetitive act of signing, sealing and stamping, you write the last person’s name on the next person’s envelope by mistake. Perhaps it explains why marathon walkers at the Olympic games cannot stop at the finish line, but carry on for at least another half lap; why your radio carries on playing for a second or two even after the plug has been pulled out; or why tonguetwisters trip us all up as the brain struggles and fails to make the mouth form different vowel shapes in quick succession. Perhaps hysteresis accounts for the instances of wafer-less, solid chocolate Kit-Kats, caused by momentary lapses on the assembly line, or explains how, in attempting to delete ten emails and preserve one, your momentum gets ahead of you and you delete them all before you can stop yourself. As explanations go, I certainly prefer it to sod’s law, although I think I understand it less well.