It may therefore lie dormant, indeed the driver may not even identify feelings of frustration. However failure to indicate or a poor manoeuvre by another driver may be enough to trigger a release of the pent-up frustration which is directed towards the offending driver. In addition, there are a number of factors that explain why driving, in particular, should cause this frustration to manifest. Studies of animal behaviour have shown how rats and various primates can respond aggressively in response to overcrowding. It is reasonable to suggest that humans respond in a comparable manner.
Human beings are territorial.
As individuals we have a personal space, or territory which evolved essentially as a defence mechanism - anyone who invades this territory is potentially an aggressor and the time it takes the aggressor to cross this territory enables the defender to prepare to fend off or avoid the attack. This may extend no further than a matter of a few feet or less. The car is an extension of this territory. Indeed, the territory extends for some distance beyond the vehicle, again providing room for the defender to prepare to fend off or avoid the attack. If a vehicle threatens this territory by cutting in, for example, the driver will probably carry out a defensive manoeuvre.