For our purpose, it is feasible to take into account just the homo sapiens sapiens species. Rationality, or the acting reason, has its’ boundaries indeed. Limitations of rationality, as we have seen in the definition problem, are properly described by Jon Elster (1986). For our purpose, it is satisfactory to keep in mind the basic problems of rational thought such as the possibility of more equally valid rational solutions, inability of ranking several outcomes or the unfeasibility of all opportunity costs calculation.
The above-mentioned problems are always conveyed in practical life. Damasio describes a patient with ventromedial prefrontal damage, who would drive his car on an icy winter day with unbelievable tranquility, following certain proper rational procedures for safety. But his pure rational thought lacking emotions did not allow him to decide simply on the next visit to his doctor. He would be trapped for half-hour in enumerating reasons for and against each of the two dates...

2.2 Emotions, Emotional Reactions
Emotions are, according to Encyclopaedia Britannica (EB), “distinct feelings or qualities of consciousness, such as joy or sadness, that reflect the personal significance of an emotion-arousing event.”
As opposed to the rational thought, emotions cannot be called up voluntarily, on the contrary, they are said to arise unconsciously. This can be illustrated by an example of ‘smile’. If we try to smile just for the sake of smiling, we use different facial muscles than those that would be used during natural smiling. Primary emotions, as seen by Damasio (2000), are emotions not controlled by reason, e.g. those “wired in” at birth. The most important example is fear. Secondary emotions, by contrast, are controlled primarily by the frontal cortices, which invoke emotional responses in response to thoughts rather than percepts. Good example: anger.
From the neurobiological point of view, emotions are regarded as evolutionary older response system of the brain as compared to the conscious rational thought. They are studied by neuroscience with regard to the connections to physiological and cortical brain states. With emotions, we can more easily anticipate the future and learn more effectively (they serve as signals). The emotional response systems involve activation of the old brain core, i.e. the subcortex. Secondary emotions, however, engage the subcortex as well as the neocortex.