To support his analysis of emotional expression, Darwin quotes several authors who presume that tears are part of the mechanisms that participate in the regulation of eye pressure. They can be associated to a variety of emotions (Darwin mentions laughter) and can sometimes be provoked by nonemotional reactions like violent coughs and yawning.75 It is possible that this nucleusâ could have been associated with sadness for generations and could have finally become genetically transmissible. It is even possible that the attitude of parents could have participated in the construction of this association. For example, if they perceive tears as an expression of sadness, the infant may discover that tears are useful to convey his sentiment of sadness. In this example, Darwin describes an association between body and emotions that is constructed in two stages:
1. There exists a reflex that still has or had a function that has nothing to do with the emotions.
2. An emotion ties itself to available body reactions without any necessary functional links between the two.
Contrary to the instincts, there is therefore no covariation between the history of one part of the body and the affect that associates itself to it.
Today, physicians clearly distinguish between tears and the aqueous humor that rinses the interior of the eye socket. Only the aqueous humor has an influence on the ocular tension. Tears would therefore not have the function of protecting the eye from changes in pressure but only that of keeping the surface of the eye clean. On the other hand, physicians still think that respiration influences both the tears and the ocular pressure.76 This complicates Darwin’s analysis a bit. But it also confirms it because, finally, the inclusion of tears in the expression of sadness, distress, joy, and anger touches functions still less central than Darwin thought. Whatever are the underlying mechanisms of tears, it is undeniable that a profound activation of respiration stimulates tears. Emotions also often activate such deep breathing. Therefore by grouping existing heterogeneous mechanisms, emotions produce a series of impacts on self and on those around us.77