Experts from the University of California, recently investigated the probability of tangling & knotting of cables, the type of knots formed and the dependence on string length in their study.
They confirmed that ‘complex knots often form within seconds’ and that stiffer wires are only slightly less likely to form such perplexing tangles.
When shaken up or agitated, the wires form overlaps and coils so that the loose end weaves though the other strands, creating the annoying knots.
Professor Robert Matthews from Aston University then set out to investigate this so-called ‘Murphy's Law of Tangles’. Basically, Matthews said that any cables that can get into knots, will do! He concluded that string - and headphones - really does have a perverse tendency to knot spontaneously and he also found that longer cables are more likely it is to spontaneously knot.