Ever thought how 'Habits' work?

We have had some time to think about things in depth the last few weeks. 🧐
And one of the things I was thinking about, were "Habits"... we all have them. But with the Corona, we have all had to break our habits in one way or the other. 

Or I did anyway ! 
But have you ever thought about habits and what they are to the horse?
 

Habituation is the process whereby the horse becomes accustomed to a stimulus and ceases to react.
It is a simple form of learning and is found throughout the animal kingdom. 
 

Because evolutionary survival depends on how efficiently animals utilise their resources, habituation is a learning mechanism that prevents animals from wasting energy in running away or avoiding things in their environment that are harmless. 

* In the natural state, animals habituate to other harmless species, and to such things as windblown foliage and shadows.
*In the domestic situation, horses habituate to features of their environment, such as cars, trains, low-flying planes, dogs, children on bikes, and rustling plastic bags. 
As in : The police horses that calmly stand in front of screaming crowds at the football have been carefully habituated to the many different stimuli they may encounter in their daily work.
 

Some stimuli are quite challenging. If the stimuli have one or more of the following characteristics, habituation may be slow or difficult to achieve.

If the stimulus:
- is too strong or painful (e.g., the shock from an electric fence);
- is new (e.g., camels or emu);
- is too close (e.g., electric clippers inside the ears);
- appears suddenly (e.g., kangaroos jumping out of nearby bushes);
- moves, especially if it moves erratically or moves towards the horse (e.g., a child with an umbrella)

I'm sure we all recognise this in one way or other.
But I was wondering how it is with your horses?
What has your horse learned to habituate to? Curious to know ...