Disputing earlier theories which say that babies develop signs of jealousy during what are called the terrible twos, a new study shows they exhibit this emotion even before they can crawl. Maria Legerstee, professor of psychology at York University here, has found that babies as old as three months react negatively when their mothers' attention is distracted by someone else. As part of her study, she said she picked up infants of ages three, six, and nine months. Their mothers sat close by as a female researcher interacted with them. Legerstee said the infants reacted negatively - looking sad, smiling less, and looking away - when the researcher did not show interest in communication. And when the researcher was busy, infants didn't mind. However, when the researcher engaged in conversation with mom, deliberately excluding baby, the result was surprising. Babies did not like that at all,'' she said. No matter what the age, they got very upset and did all kind of things to get our attention. They kicked their legs, yelled out loud, and turned in their seats. I've never seen anything like it,'' added Legerstee. According to her, all non-basic'' emotions such as jealousy, embarrassment, pride and guilt are thought to develop during the second year of life. The established notion was that an emotion like jealousy is too complex for the basic cognitive abilities of infants," said Legerstee. Jealousy implies the formation of a social bond, and is a reaction to the presence of one who threatens this bond. Thus at three months infants are aware of other people. This is strong evidence that infants understand that motives or goals guide our communicative behaviour,'' she said. The study is part of Legerstee's research into infants' socio-cognitive development, a university statement said.