DISCUSIÓN GENERAL

A major role of the frontal lobes is to exert executive control (Badre and D’Esposito, 2009). A method of exerting executive control over the brain is through cognitive inhibition. Research has shown that the executive control and inhibition exerted by the frontal lobes is key to decision-making and impulse control (Bechara and Van der Linden, 2005; Krawczyk, 2002). Inhibition and impulse control may play an important role in driving. For example, a lack of the inhibition and impulse control provided by the frontal lobes may lead to drivers speeding, pulling out at roundabouts or overtaking other cars when it is not appropriate or safe to do so. Krawczyk (2002) reported that an important function of the DLPFC is to combine multiple sources of information in order to guide behaviour and actions. As safe driving is a process of using multiple sources of information to guide driving behaviour, it is important to explore the role that the frontal lobes play in driving.

As mentioned in Chapter 4, numerous studies have shown that one of the major functions of the frontal lobes is to provide inhibition. The role of inhibition is to prevent behaviours that may be detrimental and, in terms of driving, such behaviours may have very serious consequences. Research has also shown that inhibition plays an important role in driving. There has been particular focus on how a lack of inhibition is involved in unsafe driving.

O’Brien and Gormley (2013) investigated the role that impulsivity and inhibition play in the dangerous driving of young people. They compared the performance of young drivers who had committed speeding offences with non- offenders in Stop-signal and Go/no-go tasks (both of which are inhibitory measures). While no differences between the two groups were found in the Stop- signal task, significant differences were found with the Go/no-go task. Offenders were found to exhibit lower inhibitory skills on the Go/no-go task as they made more errors on the Go tasks than non-offenders. However, offenders also responded more quickly on the Go tasks. The authors interpreted this as being the result of a speed-accuracy trade-off. This research suggests that a lack of inhibitory abilities may be a factor dangerous driving and road offences.

Research has also focused on how alcohol increases dangerous driving behaviours by diminishing the ability to inhibit risky behaviours. Fillmore,

Blackburn and Harrison (2008) studied the effect that alcohol had on risky driving behaviour. The researchers wanted to investigate how the inhibitory impairing effects of alcohol can be exacerbated by situations of conflict in which the inhibition and expression of dangerous behaviours are equally motivating. They had subjects complete a go/no-go task to measure inhibitory control and a simulated driving task to evaluate driving behaviour. Driving performance was gauged using measures such as lane deviations, vehicle impacts and stopping at traffic lights. The participants were provided with monetary incentives for these tasks for slow and careful behaviour (e.g. slow driving and inhibiting impulsive behaviour), as well as for fast and abrupt behaviour (e.g. fast driving and disinhibition) in order to produce conflicting motivations. They reported that alcohol consumption interacted with conflict to diminish inhibitory control and to increased dangerous driving. The participants who displayed the worst driving were the participants whose inhibitory control had been most affected by the alcohol, demonstrating that inhibition is vital for safe driving.

Cheng and Lee (2012) investigated the relationship between response inhibition, risk-taking and the driving behaviour of motorcyclists who had different levels of impulsivity. Response inhibition was measured using a Stroop test, impulsivity was measured using the Barratt Impulsiveness Scale, risk taking was assessed using the Balloon Analogue Risk Task and risky driving behaviour was measured with a Rider Driving Violation scale (which consisted of a self- report scale on driving violations committed). The results of the study revealed a significant relationship between response inhibition, impulsivity and risk taking. Motorcyclists with higher levels of impulsivity displayed lower levels of response inhibition and greater risk taking. Motorcyclists with high or medium levels of impulsivity were five times as likely to be involved in accidents as those with low impulsivity. This study demonstrates that drivers with higher levels of response inhibition are safer drivers and are less likely to be involved in crashes.

Cheng, Ng and Lee (2012) investigated whether motorcyclists with a history of driving offences would make riskier driving decisions and engage in more risk taking as a result due to poor response inhibition and impulsivity. Motorcyclists who had been responsible for an accident and who had at least 6 points on their licence were compared to motorcyclists who had not committed any offences. Response inhibition, impulsivity and risk taking were measure in the

same way as the Cheng and Lee (2012) study while risky decision-making was measured using a simulated motorcycle Go/no-Go task. In this task the participants had to decide whether or not to abruptly switch from the right lane to the left lane of a roundabout (which was occupied by a bus) in order to make a left turn. The authors reported that the motorcyclists with a history of offences differed in terms of response inhibition, risk taking and risky driving. The offenders displayed worse response inhibition and a greater willingness to take risks. They did not differ in terms of impulsivity though, with the authors attributing this to problems with the self-report method used. Again, this study provides evidence that levels of response inhibition are associated with how safe and accident-prone drivers are.

As mentioned in Chapter 1, one of the major findings in driving research is that young drivers are overrepresented in crash and fatality statistics. Research has also shown that adolescents and young adults lack inhibition, are impulsive and they engage in more risk taking and dangerous behaviours (Weinberg, Elvevag and Giedd, 2005; Steinberg 2008). It is possible that the increased crash and fatality rates of young drivers is in part related to their lack of inhibitory abilities, which may in turn indicate the role that inhibition plays in driving.

Together, these studies reveal the important role that inhibitory control plays in driving. High levels of response inhibition are associated with safer driving, reduced likelihood of being involved in an accident and the lower likelihood of committing traffic offences. Conversely, poor response inhibition is associated with dangerous driving, a higher likelihood of being involved in an accident and a higher likelihood of committing traffic offences. So far there have not been any studies that have used NIRs to investigate inhibition in driving.