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From a physiological point of view, a reduction in the activation of the central nervous system is observed. During a monotonous task, the electro-encephalogram (EEG) shows a marked increase in the alpha and theta rhythms typical of a reduction in wakefulness level. A reduction in the heart rate of about 30% and a reduction in blood pressure are also observed.
Taken to the extreme, monotony can lead to psychological disorders causing stress and acute fatigue. The stress would be related to the constant effort required to maintain a sufficient level of arousal to execute the task.       
6.3.2. FACTORS INCREASING THE DEGREE OF MONOTONY

6.3.2.1. ENVIRONMENT

Generally speaking, all situations lacking sensorial stimulations or with stimulations which largely remain constant, lead to a state of monotony favorable to a reduction in wakefulness level irrespective of the time of day and this, even when there is no sleep loss.
 
Several environmental factors can reduce alertness levels
 
. Repetitive or low-intensity sensorial simulations

. Reduced visual field

. Restriction in the liberty of movement (no change in postures)

. Rare social interactions

. High temperature

. Low lighting intensity

 

                                              
6.3.2.2.    MONOTONOUS TASKS 

 

Distinctions should be made between two types of monotonous tasks:
– repetitive activities,

– monitoring continuous processes. 

 

Repetitive activities are associated with work mechanization and especially its fragmentation into simplified operations. The degree of monotony of these tasks can be influenced by different factors:
– low number of actions to be repeated per time unit,

– simplicity of the actions,

– imposed rhythm. 

 

The development of supervisory activities is to be seen in relation to the development of automation. The degree of monotony of these tasks is mainly influenced by:
– a reduced visual field (night flying, observing cathode ray tubes),

– the small amount of useful information received per unit of time.     

6.3.3. MONOTONY & LONG-HAUL FLIGHT 

 

Monotony is one of the most important constraints in aviation, primarily during long-haul flights. This constraint might be accentuated when these flights are made on new-generation glass cockpit aircraft.
 
This was studied from experiments conducted by LAA and Airbus in real flight situations with voluntary crews from several participating airlines. Variations in alertness levels in flight were assessed from electro-encephalograms (EEG) and electro-oculograms (EOG). Crewmember activities and behaviors were simultaneously observed by means of an Aircrew Data Logging System. Sleep duration and quality before the rotation, during layover and after the rotation were also determined from recordings made with wrist actometers and from sleep logs (see chapter 6-2).
　
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