Harriet Over and Malinda Carpenter of the Max Planck Institute in Munich, Germany, found that priming infants with subtle cues to affiliation increases their tendency to be helpful.
The researchers showed a large group of 18-month-old toddlers photographs of household objects, such as a teapot or a shoe. The household objects were always the central image and the only thing the researchers talked about with the infants, but in the background were much smaller secondary images intended to prime the infants' subconscious thinking.
Some of the background images had two small wooden dolls, facing and almost touching each other, others had the dolls facing away from one another, while others saw just one doll and still others saw some wooden blocks.
After the children saw the images, one of the researchers "accidentally" dropped a bundle of small sticks and noted which infants spontaneously reached to help.
The study, published in the Psychological Science, found the children who had been primed for affiliation -- because they saw the background images of the dolls engaged -- were three times as likely as any of the other infants to offer help spontaneously.