Ở đầu kia của liên tục nói dối ám ảnh cụ thể, trong đó có kỷ đầu tiên khởi phát, dự toán di truyền thấp nhất và cao nhất ảnh hưởng đến môi trường cụ thể. Họ kết luận: "Tính di truyền ước tính trách nhiệm của ám ảnh. . . chỉ ra rằng yếu tố di truyền đóng một đáng kể nhưng không có nghĩa là vai trò áp đảo | 254 PHOBIAS environmental influences. At the other end of the continuum lie the specific phobias which have the earliest age of onset the lowest heritability estimates and the highest specific environmental influences. They conclude The estimated heritability of liability of phobias . . . indicates that genetic factors play a significant but by no means overwhelming role in the etiology of phobias. Individual-specific environment appears to account for approximately twice as much variance in liability to phobias as do genetic factors. Overall genetic factors appear to be associated with a general state or propensity toward fearfulness although Stevenson et al. 45 question this conclusion with high fearful albeit not phobic children whereas the environment plays a stronger role in making an individual afraid of say snakes rather than heights or enclosed places. Specificity is afforded by the environment 2 . Along with genetic factors constitutional . temperament characteristics of the child may play a role in the onset and maintenance of phobias in children. Temperament refers to stable response dispositions that are evident early in life observable in a variety of settings and relatively persistent across time 46 47 . Two of the most important temperamental categories are based on responses or initial reactions to unfamiliar people and novel situations frequently referred to as shyness versus sociability introversion versus extroversion or withdrawal versus approach . In unfamiliar situations or upon meeting new people shy or inhibited children typically withhold responding or interrupt ongoing behaviour show vocal restraint and withdraw. In contrast sociable and uninhibited children typically seek out novelty engage in conversation smile and explore the environment around them. Data from Chess and Thomas New York Longitudinal Study 46 show that these tendencies to approach or withdraw are relatively enduring dimensions of behaviour. In recent years Kagan and .
