People who share drug-injecting equipment put themselves at increased risk of developing HIV, hepatitis and other infections. It is thought that a third of the cases of HIV in the U.S. are due to injecting drug use and around 60-80% of injecting drug users are thought to be infected with hepatitis C. A team of researchers from Baltimore used a test similar to the puzzle Tower of Hanoi* to test the planning abilities of 225 injecting drug users. They wanted to see whether poor planning abilities were linked to an increased tendency to share needles. The researchers found that poor performance on the logic puzzle was associated with an increased chance of sharing needles suggesting that poor planning on the part of drug users plays a part in increasing needle sharing.
Severtson, Stevan G. ... [et al] - The association between planning abilities and sharing injection drug use equipment among injection drug users in Baltimore, MD Journal of Substance Use October 2009, 14(5), 325-333
*You can find out more about the Tower of Hanoi logic puzzle at