Anger In Infants And Its Effects On Behavioral Development

Anger is considered as one of the basic emotions in human besing. It is uncertainty whether anger emerge in four-month infants (i.e., Camras et al., 2007; i.e., Stenberg & Campos, 1990). From the valence of emotion, anger is a negative emotion (Rothbart, 1989). However, according to the theory of approach and withdrawal motivation (Fox, 1991; Gray, 1987), anger, like happiness, is considered as an basic emotion related with approach systems. Anger activiates individuals to remove barriers and orient toward goals (Campos et al., 1989; Darwin, 1872). Previous studies showed that angry children in frustration showed a lot of approach behaviors in response to novel sitimuli (Derryberry & Rothbart, 1997; Fox, 1989; Kochanska et al., 1998). However, few studies addressed the issues whether angry infants exhibit approach behaviors in frustrating situations. Anger reflecting approach tendency may be detrimental for the development of effortful control and behavior problems. Some studies reported that anger was negatively related with effortful control (Derryberry & Rothbart, 1997; Kochanska, 2003) and positively related with behavior problems (Eisenberg et al., 2007; Smeekens et al., 2007) in school-aged children and adolescents. However, few studies examined the relations between infants' anger and effortful control and problem behaviors in childhood.At physiological level, according to approach-withdrawal model of frontal Electroencephalogram (EEG) asymmetry, anger is related to left frontal EEG asymmetry with approach tendency (Fox, 1991; Harmon-Jones, 2004). However, it remains unknown if this association is also evident in high anger-prone infants, or whether anger, associated with frontal EEG asymmetry is linked to approach behaviors, effortful control or behavioral problems. As noted in approach and withdrawal models of temperament, infants responding with negative reactivity to novel stimuli manifested withdrawal and behavioral inhibition, and infants with positive reactivity pattern showed approach, sociability and exuberance in later childhood (Fox et al., 2001; Hane et al., 2008). This temperament might influence anger development and the prediction from early anger to later behaviors.In the context of a longitudinal study of temperament, this study examined the development of anger and its influences of temperament. In addition, it sought to examine the contribution of anger, combined with frontal EEG asymmetry or temperament, to approach behaviors, effortful control and behavior problems in early childhood. Two hundred and ninety-one four-month-old infants were selected from temperament patterns including affect and motor reactivity to novel stimuli (103 positive reactivity, 105 negative reactivity and 83 control group). Infants' anger expression was observed during arm restraint at both 4 and 9 months of age. Anger expression was coded using the Facial Action Coding System (FACS; Ekman, Friesen, & Hager, 2002). Infants' approach behaviors were measured during arm restraint (struggling) and an unpredictable toy task. The baseline frontal EEG asymmetry (F3. F4) at 9 months of age were assessed. Children's inhibitory control during a Go/No-Go task (GNG) was also collected at age 4. Mothers reported children's effortful control, pleasure, sociability and shyness from Colorado Children's Temperament Inventory (CCTI; Buss & Plomin, 1984) at age 3 and 4 and from Children's Behavior Questionnaire (CBQ; Rothbart, et al., 2001) at age 4, and rated children's problem behaviors from Child Behavior Checklist (CBCL age 1.5 to 5; Achenbach & Rescorla, 2002) at age 2 and age 4.The pattern of anger expression is universal across cultures both in adults and children (Ekman et al., 2002). However, one-year-old Chinese children expressed less anger than Americans (Camras et al., 2007). It is necessary to examine if this difference shows up in early of four-month age. Therefore, the anger expression of the four-month-old Chinese infants (n = 32) and American infants (n= 21) were compared during arm restraint and in maternal report. Furthermore, it is investigated whether the relation of anger and approach behavior is still found in Chinese sample.The results indicated that: 1) The infants' anger expression increased from 4 months to 9 months among those infants selected for positive reactivity but not negative reactivity temperament; 2) During the arm restraint at 4 and 9 months, high frequency of anger-prone infants exhibited more and stronger struggling than low frequency of anger-prone infants, especially in infants with low and moderate intensity of anger; 3) High frequency of anger-prone infants at 4 months with 9-month left, but not right, frontal EEG asymmetry showed more 9-month approach behaviors and less 4-year inhibitory control relative to low frequency of anger-prone infants; 4) In positive reactivity temperament pattern, 9-month high frequency of anger-prone infants had higher 4-year effortful control and lower 2-year internalizing behaviors than low frequency of anger-prone infants; 5) There was also moderate stability of anger frequency from 4 months to 9 months. Continuously high anger-prone infants across ages displayed more happiness, activity, sociability and less shyness from maternal report of CBQ at age 4 and CCTI at age 3 and 4 than continuously low anger-prone infants; 6) Chinese infants displayed less anger than American infants during arm restraint and in maternal report; 7) In Chinese infants, high intensity of anger was linked to high intensity of struggling; while in American infants, high intensity of anger was linked to low intensity of struggling.In conclusion, anger expression has emerged by 4 months of age, and increased from 4 months to 9 months. It offered great evidence suggesting the long term implications of anger with approach tendency in early infancy for approach behaviors, effortful control and behavioral problems in early childhood, and these associations were also influenced by infants' frontal EEG asymmetry and temperament. More importantly, it addressed the evidence that Chinese infants expressed less anger than Americnas early at 4 months.