According to a new research, children's saliva could show their anxieties about relationships with parents or teachers. U.S. researchers found that a stress-linked enzyme, alpha amylase, marks the sympathetic nervous system's response to certain social factors. Among these social factors which caused stress in the tests were babies being gently restrained by a stranger and older children being asked to complete a frustrating task or being evaluated. Children's relationships with their parents or teachers also influenced the levels of alpha amylase. The researchers found a chemical connection between mothers and their babies, these and their 6-month-old baby boys having the same levels of this enzyme. Dr. Douglas A. Granger at Pennsylvania State University found that 4-year-old children with higher alpha amylase levels were more susceptible to illness and had less close relationships with their preschool teachers. Among children of 8 and 9 years of age, high alpha amylase levels were associated with aggressive behavior and cognitive/academic problems. "Being able to monitor alpha amylase via a salivary test may open new opportunities to characterize individual differences in response to stress that we weren't able to see before. We think that these differences could prove to be meaningful in understanding behavior," Granger stated. The tests of alpha amylase were developed by Granger and a team of researchers at his company, Salimetrics LLC.