Right before you work up the nerve to leap off a bungee-jumping platform and plummet toward the Earth, there will be a sharp, measurable increase in your brain activity—almost a full second before you make the conscious decision to jump. A new paper in Scientific Reports purports to describe the first time this effect has been measured outside the laboratory.
That telltale signal was dubbed bereitschaftspotential (BP)—or "readiness potential" in English—when it was first observed in 1964 by Luder Deecke and Hans-Helmut Kornhuber. Kornhuber and Deecke had subjects make hundreds of voluntary finger movements while otherwise sitting as still as possible in a Faraday cage. The researchers noticed a shift in the electrical voltage in the brain, as measured by electroencephalography (EEG) electrodes placed along the scalp. The effect is often cited in the ongoing, heated debate over whether or not humans truly have free will.
The German and Austrian authors of the current study opted to have their subjects go bungee jumping in hopes of recording this readiness potential. While bungee jumping has its roots in an ancient ritual on the South Pacific island-nation of Vanuatu as a way to test one's courage, prior studies have shown it results in a sharp rise in concentrations of beta-endorphins right after jumping. (This spike is despite the fact that, the authors note, bungee jumping is statistically less life-threatening than more common activities like bicycling or dancing. Our impulse reactions are not rational.)