Those addicted 0) to painkillers 1) .... not find babies cute. While this may not seem a big deal, doctors claim this is a dangerous sign of 2).... drugs can manipulate the brain. The human tendency to  find babies cute stems 3).... our drive to nurture and protect, but a study by the University of Pennsylvania (USA) found that babies do not trigger any emotional reaction 4) ... addicts. The researchers said that drugs derived from opium that are prescribed for pain are some of the most common medications  in the world, but they appear to change the motivation to care for 5) ... and could mean a more serious cognitive imbalance. Addiction to opioids, both illicit drugs such as heroin and pain treatments, affects 6) ..... four million people in the USA. Their use is associated with reduced responses to natural rewards, as well as abnormal social behaviour but could 8) .... affect basic human instincts, according to the study.