learning In the 2000s, studies suggest that eye contact has a positive impact on the retention and recall of information and may promote more efficient learning. Maternal sensitivity In a 2001 study conducted in Germany examining German infants during their first 12 weeks of life, researchers studied the relationship between eye contact, maternal sensitivity, and infant crying to attempt to determine if eye contact and maternal sensitivity were stable over time. In this correlational study, they began by categorizing the mother's sensitivity placing them into one of four behavioral categories: inhibited/intense behavior, distortion of infant signals, over and understimulational, and aggressive behavioral. Next, the observer video-taped the mother and infant's free-play interactions on a weekly basis for 12 weeks. When watching the videos, they measured the mutual eye contact between the mother and the infant by looking at the overlap in time when the mothers looked at their infant's face and when the infants looked at their mother's face. The mothers were also asked to record their infant's crying in a diary. The study found that the amount of eye contact between the study's German mothers and infants increased continuously over the first 12 weeks. The mother who held eye contact with her child early on (week 1–4) was described as sensitive to her infant whereas if she did not hold eye contact, her behavior was described as insensitive. They also found a negative relationship between eye contact and the duration of crying of the infants; as eye contact increases, crying decreases. Maternal sensitivity was also shown to be stable over time. According to the study, these findings may potentially be based on the assumption that sensitive mothers are more likely to notice their child's behavioral problems than non-sensitive mothers. Difficulty Some people find eye contact difficult with others. For example, those with autism spectrum disorders or social anxiety disorders may find eye contact to be particularly unsettling. Strabismus, especially esophoria or exophoria, interferes with normal eye contact: a person whose eyes are not aligned usually makes full eye contact with one eye only, while the orientation of the other eye deviates slightly or more. Eye aversion and mental processing In one study conducted by British psychologists from the University of Stirling among 20 British children at the age of five, researchers concluded that among the children in the study, the children who avoid eye contact while considering their responses