Scene and Task
The client is driving along a straight highway. At irregular intervals other vehicles come towards him on the opposite carriageway or overtake him. The client’s task is to react by pressing a button when an overtaking vehicle suddenly brakes in front of him. Once he has reacted the vehicle’s brake lights go out and it accelerates away from him. If the client fails to react within the permitted time, the brake lights start to flash. Eventually there is a loud squealing noise, which is designed to draw the client’s attention to what is happening.
Theory
Long-term alertness tasks require the client’s attention “to be focused continuously for long periods of time on one or more sources of information, in order to detect and respond to small changes in the information presented” (Davies et al. 1984). Vigilance represents a special variant of long-term attention. Vigilance tasks make demands on attention over a long period of time – often a number of hours – and the relevant stimuli typically occur at very irregular intervals and at a very low frequency among a large number of irrelevant stimuli. Vigilance training cannot be effective unless a training session lasts for more than 30 minutes at the minimum.
Difficulty
The VIG training program has 30 difficulty levels. A decreasing stimulus frequency makes it more and more difficult for the client to sustain his attention: he is overtaken by other cars increasingly rarely, the surroundings become more monotonous as darkness falls and the number of sudden braking manoeuvres from overtaking vehicles decreases. In addition, the intensity of the feedback on delayed and omitted reactions becomes weaker as the difficulty level increases. The challenge therefore changes gradually from a sustained attention task to one requiring real vigilance.
At each difficulty level the maximum permitted reaction time adapts to the speed of the client’s reactions. Taking the client’s first valid reactions as a starting point, an individual reaction time limit is determined and used as a basis for measuring all further reactions made in the course of the training program. This ensures that from the outset the training program is optimally adapted to the client’s skill and is never either too easy or too difficult for him.
Note
VIG can also be used with patients with impaired field of vision.
