Scientists have said shining a light on eggs for at least 12 hours a day can make chickens 'calmer' and 'less fearful'.Researchers at the University of California, Davis bathed eggs daily in light for different time periods during their three-week incubation.When the chickens reached 3 to 6 weeks old, the scientists tested the birds’ fear responses.In one test, 120 chickens were randomly selected from the 1,006-bird sample and placed one by one in a box with a human “predator” sitting visibly nearby.The chickens incubated in light the longest — 12 hours — made an average of 179 distress calls in three minutes, compared with 211 from birds incubated in complete darkness, animal scientists Gregory Archer and Joy Mench report in January in Applied Animal Behaviour Science.Chickens exposed to lots of light as eggs “would sit in the closest part of the box to me and just chill out,” Archer says.The others spent their time trying to get away. How light has its effect is unclear. On commercial chicken farms, eggs typically sit in warm, dark incubation rooms. The researchers are now testing light's effects in large, commercial incubators. Using light exposure to raise less-fearful chickens could reduce broken bones during handling at processing plants, Archer says. It might also decrease harmful anxious behaviours, such as feather pecking of nearby chickens.