Humans display the largest web of connections between the prefrontal area and the traditional limbic structures. Perhapas that is why they present, among all species, the greatest variety of feelings and emotions Although some signs of affection can be perceived in birds, the limbic system only began to evolve, in fact, after the first mammals, being practically non-existent in reptiles, amphibians and all other preceding species.

Paul MacLean uses to say that "it is very difficult to imagine a lonelier and more emotionally empty being than a crocodile". Two behaviors, with affective connotation, that appeared with mammals (birds also display them, but less intensely) deserve to be emphasized because of their peculiarity :

1 - The intense and long-lasting care and nursing of females towards their offsprings.

2 - A playful mood. The more evolved the mammal, the more accentuated are these behaviors.

Ablation of important parts of the limbic system of any animal causes it to loose, totally, both motherly affection and ludic interest.

And the evolution of mammals bring us to mankind. Certainly, our hominid ancestor could already establish differences between the sensations he experienced in distinct occasions, such as being at his cave polishing a stone or a bone, running after a weaker animal, running away from a stronger one, hunting a female of his species etc.

With the development of language, particular names were given to these sensations, allowing their definition and communication to other members of the group. Since there exists an important subjective component, difficult to be communicated, even today there is no uniformity concerning the best terminology to be used, in order to designate, specifically, many of these sensations.

Therefore, the words affect, emotion and feeling are used interchangeably and imprecisely, almost like synonyms. However, we think that each of these words deserves a precise definition, for the sake of their etymology and because of the physical and mental reactions they cause.

Affect (from the Latin affectus meaning to afflict, to shake, to touch) could be defined as "a grouping of physic phenomena manifesting under the form of emotions, feelings or passions, always followed by impressions of pleasure or pain, satisfaction or discontentment , liking or disliking, joy or sorrow".

Curiously, there is a worldwide trend to consider as affect (as well as its derivatives, like affection, affectuous, etc.) only the positive impressions. Thus, when I say : "I feel affection for that girl", I'm expressing love or tenderness, never anger or fear. Counterwise, emotions and feelings can be used to name both positive and negative phenomena : "she has good feelings; I've had painful emotions".

According to Nobre de Melo, affect denominates, generically, events experienced as emotions or feelings. Emotions (from Latin emovere meaning moving, displacing) are, as its etymology suggests, manifest reactions to those affective conditions that, due to their intensity, move us to some kind of action. Confronting the opinion of several authors, we can say that emotions are characterized by a sudden disruption of the affective balance.

Almost always, they are short episodes, with slight or intense, concomitant or subsequent, repercussions upon several organs, that can set up partial or total blocking of logical reasoning. This can provoke, in the affected subject, a high degree of psychic and behavioral loss of control. Conversely, feelings are seen as affective states with a longer duration, causing less intensive experiences, with much fewer repercussions upon organic functions and lesser interference on reasoning and behavior.

Exemplifying : love, fear and hate are feelings; passion, fright and anger (or wrath) are emotions. There also exist two other well characterized conditions that are, in a certain way, inserted in the context of affective life (since, depending on the intensity of the affect, these two conditions may result from the affective state or, sometimes, can be mistakenly considered as an emotional manifestation).

We are talking about mood disturbances (represented by depressions or maniacal euphoria) and the lessening of mental relaxation associated to the alert reaction (represented by anxiety). During centuries, philosophers, physicians and psychologists studied the phenomena of affectivity, questioning their origin, their role upon psychic life, their action favoring or hindering adaptation, their neurophysiological concomitants and their neuroendocrine substratum. Affective manifestations would have as their ultimate cause, the capacity of living matter to answer to stimuli acting upon it. There are two classical and antagonistic theories upon the subject. The first one, supported by Darwin and his followers, state that affective reactions are innate patterns designed to orient behaviour in order to promote the adaptation of a being to its environment, thus guaranteeing its survival and that of its species.

The organic disturbances, that may go together with the process, would only be a consequence of physiological nature. On the contrary, others, like William James, state that, facing a given real or imaginary stimulus, the organism would react with a series of muscular and visceral neurovegetative changes.

The perception of such changes would give origin to the corresponding affective states. More recently, Lehmann proposed a third theory that suggests a compromise between the two classical ones. According to him, affect is a complex phenomenon, initiated by a central process, as result of internal or external causes. It manifests itself as a change in the "I", releasing reflex facial movements and producing manifold organic alterations.

The more the bodily symptoms increase, the more mobilizing becomes the affect, until it evolves into an emotion. This statement finds clinical support in the treatment of patients with performance phobias. When facing situations they fear (speaking before audiences, for instance) these patients present palpitations, sweating, difficult breathing, etc.. Beta blocking agents, that do not cross blood brain barrier (therefore devoid of influence upon brain centers) act only peripherally, blocking the neurovegetative symptoms and, by "emptying" anxiety, facilitate the control of the phobic process.

Divergent are also the opinions about the relationship between affective states and reason. Some philosophical and religious schools consider the affective aspects of personality as inferior, negative or sinful, in need of control and domination by reason. Claparède, in a paper bearing the title "Feelings and emotions", defines emotions as useless, unadaptative and harmful phenomena, true remains of ancestral reactions. Just the opposite of feeling, that would be useful, allowing human beings to estimate the value of things to which they must adapt and differentiating the useful from the noxious.

Quoting the author : "Observation shows how unadaptive are emotional phenomena. Emotions happen precisely when adaptation is hindered by any motive . "The analysis of corporal reactions in emotions shows that the subject does not enact adaptive movements but, on the contrary, reactions that resemble indefinite primitive instincts... "Far from being the psychic aspect of an instinct, emotion represents a confusion of this instinct ". Contrariwise, other authors consider affective reactions as factors favoring adaptation and survival, inducing some behaviours and inhibiting others. In their opinion, even intense emotions, evaluated as disruptive by others, could favour survival.

This is so because their disruptiveness is a selective one : while some actions are abolished, others, more favorable, are allowed to occur. We believe that, within certain limits, the affective participation reinforces the cognitive component, giving more flavour to the day-to-day experiences and facilitating adaptive behaviors. Nevertheless, when above these limits, emotions hamper reasoning and, when below them, as stressed by Damasio in "Descarte's error", affectivity becomes scarce, thus impoverishing the quality of life.

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