Dog lovers will have noticed several times that the gesture of caressing the animal's belly in some points triggers a rapid movement of the legs in it, as if the dog fell prey to a strong itch with an irresistible need to scratch.
The reasons for this singular behavior are to be found in the so-called scratch reflection (which in English means precisely scratching).
What is a reflection?
A reflex is an involuntary and stereotyped motor response to a particular stimulus.
In the animal world, reflexes are widespread and man is no exception; the classic example is the so-called patellar or patellar reflex, for which when the doctor beats with a hammer under the knee the leg responds by extending. As anticipated, this gesture is absolutely involuntary and this allows the organism to respond almost immediately to the danger stimulus; bypassing the will it is possible to implement very fast responses, as happens when we touch a hot object: before the brain recognizes the stimulus as dangerous, the spinal cord will have already perceived the danger and implemented the automatic gesture of retracting the hand.
The scratch reflection
The so-called scratch reflex is a defensive mechanism that aims to protect the animal from harmful insects and parasites; the fact of rapidly shaking the legs in response to the stimuli on the belly, in fact, allows the dog to defend itself from the bites of these animals.
