Optical illusions

The teacher shows these images one at a time and asks the class to indicate what they see.

At this point, he introduces the concept of perception (the definition in the glossary can be used) and explains that this concept is closely linked to that of hazard. He then illustrates a situation in which a correct perception of the situation prevents a danger from becoming a disaster:

I am at home and I smell a strong smell of gas, I realise there may be a leak so I ask my parents where the main gas tap is at home, I close it and open the windows without turning on the light.

Perception - becoming aware of a reality one considers external thanks to sensory stimuli experienced first-hand, analysed and processed through intuitive processes that allow one to adapt one's behaviour.

The teacher asks the class to identify in the typical situation just illustrated

- the danger (gas leak)

- the sensory stimulus (smell of gas)

- the behaviour adopted as a result of the sensory experience (turning off the tap, opening the window, not turning on the light)

- the disaster that could have occurred if the perception had been wrong (explosion)

The teacher shows a figure to the class in which three squares of different colours (orange, blue and green) are drawn with a red square inside each and asks the class to indicate whether the square inside each figure is the same shade of red or not (the class should see each red square of a different shade).

The teacher opens a small discussion with the class by asking what they think has changed between the first and second observation experience.

The teacher then gives an explanation of what happened: the perception of a colour can be influenced by the colour of the background. Certain colours can be emphasised by juxtaposing them with contrasting colours or be attenuated by very similar colours. Similarly, a dangerous situation can be 'less visible' if one does not have the perception and knowledge of the 'background' and diminish the awareness that anyone can be in a dangerous situation and not know how to act.

Putting on the white mask helped to get an exact view of the red hue of the squares. Likewise, knowing the dangers to which one is exposed, the behaviour to adopt and disseminating this knowledge, helps one to 'see' the situation more clearly. This means having a correct perception of the risk and thus being able to act correctly.

Do you know your environment well? Would you be able to leave the classroom with your eyes closed? With the help of the teacher, the class can test their perception of space.