at bedtime gives the infant room to learn self-soothing and self-regulation.: 24 in 2020, a finnish study established (according to the research leader) for the first time a reference value for infant sleep quality based on a large data set (about 5,700 babies). almost 40% of the participating parents with eight-month-old babies said they were worried about their sleep. in fact, sleep problems were common; however, children fall asleep faster, wake up less often during the night and stay awake less late at night the older they get. at the same time, total sleep time decreases. the study was also able to determine reference values for normal sleep (see table). children who sleep significantly less than average would usually benefit from supportive measures, for which a number of methods would be available (a discussion with the pediatrician or see, for example, the article on sleep training). age time untilfalling asleep wakingsper night waking timeper night 12 months 0–30 min 0–2.5× 0–20 min 30–40 min 2–4× 20–45 min > 40 min > 4× > 45 min 24 months 0–30 min 0–1× 0–8 min 30–45 min 1–2× 8–15 min > 40 min > 2× > 40 min key: = normal sleep = sleep hygiene should be improved = it is recommended to seek help (pediatrician, sleep counselling). maternal sensitivity maternal sensitivity plays a particular role in the relationship with the infant and for favorable emotional development. this means being attentive to the infant's behavioral expressions, not misinterpreting the infant's expressions because of one's own moods, reacting immediately to the situation and finding a response that is appropriate to the context and the expressed needs. a secure attachment is promoted through empathetic and adequate as well as prompt responses. in accordance with their basic needs, infants show an inborn behavior of seeking closeness to the mother – or to another primary caregiver – and thus in turn foster an attachment. when separated from the mother, infants protest by crying and by body movements. other an infant from uganda playing with stoves wearing has a calming effect on infants. a 2013 study showed that infants placed in a cradle cried and kicked more often and had an increased heart rate (so the infants were stressed), while those picked up and carried by the mother while walking around calmed down significantly. the effect of being held motionless in the arm was intermediate between that of being carried around and that of being put down. that carrying (e.g., in a baby sling) makes infants more content and makes them cry less had already been shown in a randomized study in 1986. for infant feeding, breastfeeding is recommended by all major infant health organizations. many airlines refuse boarding for all babies aged under 7 days (for domestic flights) or 14 days for international flights. asiana airlines allows babies to board international flights at 7 days of age. garuda indonesia disallows all babies under the age of 14 days to board any flights. delta air lines allows infants to travel when they are less than 7 days old when they present a physician travel approval letter. skywest will not allow an infant less than 8 days old on board. behaviour emotional development eight-month-old sororal twin sisters attachment theory is primarily an evolutionary and ethological theory whereby the infant or child seeks proximity to a specified attachment figure in situations of alarm or distress for the purpose of survival. the forming of attachments is considered to be the foundation of the infant/child's capacity to form and conduct relationships throughout life. attachment is not the same as love or affection although they often go together. attachment and attachment behaviors tend to develop between the age of 6 months and 3 years. infants become attached to adults who are sensitive and responsive in social interactions with the infant, and who remain as consistent caregivers for some time. parental responses lead to the development of patterns of attachment, which in turn lead to 'internal working models' which will guide the individual's feelings, thoughts, and expectations in later relationships. there are a number of attachment 'styles' namely 'secure', 'anxious-ambivalent', 'anxious-avoidant', (all 'organized') and 'disorganized', some of which are more problematic than others. a lack of attachment or a seriously disrupted capacity for attachment could potentially amount to serious disorders. infants develop distinct relationships to their mothers, fathers, siblings, and non-familial caregivers. beside the dyadic attachment relationships also a good quality of the triadic relationships (mother – father – infant) is important for infant mental health development. response to sounds infants respond to the sound of snake hissing, angry voices of adults, the crackling sound of a fire, thunder, and the cries of other infants. they have a drop in heart rate, their eyes blinking, increased turning toward the speakers or parent, all of these indicating that they were paying more attention. this is believed to be an evolutionary response to danger. babies' ability to accurately locate sounds is refined during their first year. health issues diseases further information: neonatology the infant is undergoing many adaptations to extrauterine life, and its physiological systems, such as the immune system, are far from fully developed. potential diseases of concern during the neonatal period include: neonatal jaundice infant respiratory distress syndrome neonatal lupus erythematosus neonatal conjunctivitis neonatal tetanus neonatal sepsis neonatal bowel obstruction benign neonatal seizures neonatal diabetes mellitus neonatal alloimmune thrombocytopenia neonatal herpes simplex neonatal hemochromatosis neonatal meningitis neonatal hepatitis neonatal hypoglycemia mortality main article: infant mortality an infant being immunized in bangladesh infant mortality is the death of an infant in the first year of life, often expressed as the number of deaths per 1000 live births (infant mortality rate). major causes of infant mortality include dehydration, infection, congenital malformation and sids. this epidemiological indicator is recognized as a very important measure of the level of health care in a country because it is directly linked with the health status of infants, children, and pregnant women as well as access to medical care, socioeconomic conditions, and public health practices. there is a positive relationship between national wealth and good health. the rich and industrialized countries of the world, prominently canada, the united kingdom, the united states, and japan, spend a large proportion of their wealthy budget on the health care system. as, a result, their health care systems are very sophisticated, with many physicians, nurses, and other health care experts servicing the population. thus, infant mortality is low. on the other hand, a country such as mexico, which spends disproportionately less of its budget on healthcare, suffers from high mortality rates. this is because the general population is likely to be less healthy. in the u.s., infant mortality rates are especially high in minority groups. for instance, non-hispanic black women have an infant mortality rate of 13.63 per 1000 live births whereas in non-hispanic white women it was much lower at a rate of 5.76 per 1000 live births. the average infant mortality rate in the u.s. is 6.8 per 1000 live births. babyhood babyhood is a critical period in personality development when the foundations of adult personality are laid. in contrast toddler is used to denote a baby that has achieved relative independence, in moving about, and feeding.