Personality and Accidental Injuries
Personality is defined as stable individual differences in a person’s thinking, feeling, and behavior.
Temperament is defined as genetically and environmentally influenced characteristics of reactivity to the external environment and internal self-regulation that remain stable throughout the lifetime.
Unintentional injury, first operationalized by Haddon (1980), can be conceived as damage to the body arising from the transfer of external, mechanical, thermal, electrical, chemical, or radiant energy. Injuries arising from these sources of energy often result in falls, poising, burns, choking, and motor vehicle injuries. It should also be noted that injuries can occur as a result of loss of energy, as in the case of drowning. In the past, injuries were often considered to be unavoidable and thus termed accidental. However, the overall consensus in the field is that injuries are preventable (World Health Organization 2006).
Unintentional injury ranks as the fourth leading cause of fatality in the USA and cost well over $200 billion in 2015. Unintentional injuries that do not result in death are also endemic, with an estimated 30 million people sustaining nonfatal injuries in the USA (National Center for Injury Prevention and Control 2013). The number of reported fatal and nonfatal injuries is staggering but out shadowed by the multitude of injuries that were not severe enough to warrant treatment and thus not recorded. Given the prevalence of unintentional injury and the associated costs, researchers, practitioners, and policy makers have a vested interest in understanding the many underlying contributors of injury if this public health issue is to be adequately addressed. Epidemiologists and behavioral scientists alike have identified temperament as a predominant and persistent factor that can be linked to injury. Much of the literature concerning unintentional injury and personality focuses on the interaction of child temperament and unintentional injury. This is not entirely surprising since the concepts of personality and temperament are often thought of as being very similar (Costa et al. 2001), if not inextricable. Therefore, the majority of the subsequent information found throughout this entry will focus on characteristics of temperament and their impact on injury.
Temperament, as conceptualized by Mary Rothbart (1981), is the early, yet stable, individual differences of emotional reactivity and internal self-regulation. It is comprised of three distinct categories: (1) surgency/extraversion, (2) negative affect, and (3) effortful control. Surgency (also known as extraversion) addresses traits of activity level, impulsivity, shyness, approach, and high-intensity pleasure. Negative affect concerns fear, sadness, shyness, and anger. Finally, effortful control focuses on attention and inhibitory control. Temperament is thought to be influenced primarily by genetics. However, the expression of temperament is a reaction to the environment (Wachs et al. 2001; Thomas and Chess 1977; Scarr and McCartney 1983).
The identification of child temperament, in its current conception, as a contributor to childhood injury risk has been well established, dates as far back as the 1960s (Langley et al. 1983; Manheimer and Mellinger 1967; Matheny 1987), and continues to be of interest to behavioral scientists studying injury risk and prevention. Broadly, this interest stems from the fact that due to individual differences in temperament, some children will be predisposed to seeking out new and interesting environments, whereas others will not (Scarr and McCartney 1983; Schwebel 2004). Unfortunately, some of the new and interesting environments that these children are predisposed to seek out have the potential for injury. Temperamental characteristics that are thought to increase or decrease injury risk include but are not limited to impulsivity, inhibitory control, attention, fear, shyness, and negative affect.
When considering the impact of temperament on injury, it is essential to keep in mind that there are a host of other factors known to contribute to injury that should also be taken into consideration such as environment, income, and gender. In addition, it is likely that temperament interacts with these other factors to lessen or increase injury risk accordingly. Schwebel and Barton (2005) assert that the relationship between temperament and injury is complex and consisting not only of direct pathways from temperamental characteristics to injury but also involves a mediated moderation pathway that has temperament, parenting, and physical estimation of risk working in tandem to influence injury risk.
The link between unintentional injury in childhood and temperamental traits found under the construct of surgency/extraversion is robust. For example, as part of a longitudinal study on children’s temperament and estimation of their physical abilities, Schwebel and Plumert (1999) report that children whose mothers described them as being high on extraversion had more reported past, serious injuries that required professional medical treatment. They also found that mother’s reports of extraversion were negatively correlated with physical ability estimation, with children high on extraversion overestimating their physical abilities and children low on extraversion underestimating their physical abilities. The consequences of overestimating your own physical ability have potentially injurious consequences. Take, for example, a child jumping over a log. If the child overestimates his or her ability to clear the log when jumping, the child could trip and suffer a serious injury.
More specific components of surgency/extraversion have also been linked to injury. Impulsivity refers to a hasty response to stimuli found in the environment. This particular component of surgency is driven by external stimuli found in the environment. Numerous studies have linked high levels of impulsivity with a higher number of reported injuries requiring medical treatment and minor in-home injuries (Schwebel 2004; Plumert and Schwebel 1997). It has been hypothesized that increased impulsivity leads children to act before considering the outcomes of their actions (Schwebel and Barton 2006), such as a child running across the street to meet a friend without looking to traffic first.
The contribution of hyperactivity, a facet of activity level that is often linked with impulsivity, to increased injury risk has some mixed evidence. However, data supporting a connection between activity level and injury is robust. Early studies of temperament and injury (Langley et al. 1983), which investigated the association of injuries and 7-year-old’s behavior, as reported by teacher and parent report using longitudinal data from the Dunedin Multidisciplinary Child Development Study, found links between increased injury and increased activity level. Similarly, Plumert and Schwebel (1997) report a link between children’s overestimation of physical ability among highly active children. Further, Nikolas and colleagues (2016) report that children described by parents as being hyperactive-impulsive were more likely to choose gaps that were too small to afford a safe crossing when crossing virtual roads on a bicycle. It is believed that children with increased levels of hyperactivity are at increased risk for injury due to increased motor activity.
Also considered to be a characteristic of temperament, negative affect in the form of aggression and oppositional behavior has been shown to increase injury risk. Oppositional defiance is a common comorbidity among children diagnosed with ADHD, an at-risk group where unintentional injury is concerned. However, aggressive behavior does not require a formal diagnosis in order to contribute to injury. Many studies have found that children’s and adolescents’ aggressive and overactive behaviors were predictive of later sustained injuries severe enough to warrant medical attention (Bijur et al. 1986, 1988; Bije et al. 1991; Pulkkinen 1995; Langley et al. 1983; Nyman 1987). Again, using road crossing as a model to study risky behavior, Stevens et al. (2012) found that 10-year-old boys high on aggression (via mother report) did not stop at intersections as frequently as those low on aggression, waited less before entering traffic, chose smaller gaps for crossing, cut in more closely behind the lead vehicle in the gap, and due to the small gaps they chose for crossing had less time to spare upon exit. Together, this indicates a very risky pattern of road-crossing behavior. Why might children who exhibit aggressive behavior be at increased risk for injury? According to work by Steinberg (2007), these children are more likely to show increased excitement when confronted with danger, leading to even lower levels of inhibition. Similarly, antisocial behavior is/was thought to be strongly related to hyperactivity, which could then increase risk even more (Davidson 1987; Bijur et al. 1986).
Shyness, another component of negative affect that was conceptualized by Rothbart (2007) as a “slow or inhibited approach in situations involving novelty or uncertainty,” has also been associated with injury risk. For instance, in a recent study of children’s interactions with an unfamiliar dog, researchers found that children low on shyness were more willing to approach, touch, and interact with the dog than were children who were rated as being high on shyness (Davis et al. 2012).
Effortful control, or the ability to restrain from engaging in unwanted behavior, continues to develop throughout childhood as children gain more cognitive control (Eisenberg and Spinrad 2004). Where injury is concerned, Schwebel (2004) reports that children high on effortful control are more mindful in their approach of potentially dangerous activities or objects, perceiving the dangers and exhibiting the ability to resist engaging in an activity that might be dangerous, instead choosing to engage in activities that don’t involve injury risk.
Inhibitory control, considered to be part of the broader temperamental construct of effortful control, refers to the ability to inhibit inappropriate responses to stimuli in novel, uncertain, or guided conditions and requires attentional control, cognition, and self-regulation. Inhibitory control is internally driven, unlike impulsivity which is driven by external stimuli within the environment (Eisenberg and Spinrad 2004). Parent reports of inhibitory control indicate an increased number of past injuries among children lower in inhibitory control (Schwebel and Plumert 1999). Again, an overestimation of physical ability could be the mechanism driving increased injury risk among these children, with uncontrolled children as young as 6 years overestimating their physical abilities (Schwebel and Plumert 1997). Similarly, Schwebel and Plumert (1999), using a longitudinal study of children’s temperament and estimation of physical abilities, found that mother’s reports of children having high inhibitory control at preschool and school age correlated with an underestimation of physical ability, thus playing a protective role in children’s injury risk. In contradiction to previous findings, they reported that poor inhibitory control was not found to be associated with overestimation of physical ability. However, poor inhibitory control (both as reported by mothers and measured in a behavioral task) was related to increased number of past injuries. Low levels of inhibitory control likely contribute to increased injury risk because children are not able to stop themselves from engaging in an activity that is dangerous, despite knowing the risks.
But how, specifically, do low levels of inhibitory control influence risky behavior when children are engaged in potentially dangerous activities? Only a handful of studies have addressed this question, most of which have focused on pedestrian and bicyclist road crossing. One example comes from Stevens et al. (2012). They had children aged 10 and 12 years cross a road with two-way traffic on a bicycle in an immersive virtual environment. They found that 10-year-old children high on inhibitory control timed their movement more precisely into the traffic gap and had more time to spare upon exiting the roadway compared to those low on inhibitory control. This pattern of more finely tuned road entry is like that seen in adults and indicates that children high in inhibitory control exhibit more mature road-crossing behavior than children low on this dimension. Relatedly, a study comparing the road-crossing behavior of children with and without ADHD found that when crossing roads on bike, children reported to be low in inhibitory control were less timely in their entry into the traffic gap and as a result has less time to spare when exiting the gap. As suggested by Schwebel and Barton (2006), children low in inhibitory control may not be able to plan danger avoidance appropriately. This lack of planning may help explain why movement timing is less precise in children with inhibitory control when crossing roads with traffic.
Temperament and Implications for Injury Prevention
While temperament is relatively stable throughout the lifetime, that does not mean that children high on those temperamental characteristics that increase injury risk are doomed to incur injury. Our understanding of how temperament contributes to injury has implications for injury prevention interventions. Specifically, temperament directly influences behavior, yet is variable in its expression due to the environment. This means that changes in the environment can change injury-related outcomes. One way to change the environment for highly impulsive and under controlled (i.e., low on inhibitory/effortful control) children is via increased parental supervision and/or parental presence. In another study of physical ability estimation, Schwebel and Bounds (2003) report that these children were better able to estimate their physical abilities when parents were present, while parents had no effect on children’s ability to estimate physical capabilities when children were not temperamentally impulsive or under controlled. Positive parenting and increased supervision as a protective factor against injury in temperamentally difficult children is also supported by research from Schwebel et al. (2004).
Understanding which constructs of temperament influence injury risk also allows for the targeting of interventions to those that can benefit most from them. One particular group, children diagnosed with ADHD, demonstrates this quite well. Children diagnosed with ADHD are at increased risk for injury (Pastor and Reuben 2006). The specific temperamental characteristics that have individually been linked with injury (i.e., low inhibitory control, high impulsivity, and high comorbidity of oppositional defiance) have also been identified as being associated with specific risky behaviors in the lab (Nikolas et al. 2016). Knowing that a group of temperamentally risky children can be readily identified could help researchers target this and other at-risk groups accordingly. Such focused interventions may be more successful than those that target a broader population.
The acknowledgment of temperament as a contributor to unintentional injury has a long, established history. Of the many temperamental characteristics that influence injury, impulsivity, inhibitory control, and activity level are thought to be the most significant at increasing risk in childhood (Schwebel and Barton 2006). To date, much of the evidence linking temperament to injury risk is correlational in nature. The need for studies to investigate the causal nature of temperament is apparent. However, the evidence is overwhelming, and interventions targeting those at greatest risk for injury due to temperament are few but promising.
- National Center for Injury Prevention and Control. (2013). WISQARS (Web-Based Injury Statistics Query and Reporting System). Retrieved from http://www.cdc.gov/ncipc/wisqars
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