**5. Possible relationships between contagious laughter and happiness**

Although it is clear that happiness is a multidimensional concept that includes several levels, such as life satisfaction, satisfaction with the achievement of goals, and the subjective feeling of well-being, etc. (e.g. [57, 58]), the authors who have delved into the subject agree that one of its main components is the hedonistic, that is, its relationship with pleasure and joy [58] and it is precisely this component that would be related to contagious laughter.

In addition to the fact that frequent laughter is one of the most recognized expressions of joy/happiness [10], which would show its hedonic nature, the relationship that would exist between happiness and contagious laughter would be based on three additional aspects: (a) the tendency of the human being to experience positive affect by default, which would be the basis of both [59, 60]; (b) the fact that both laughter and happiness have positive emotions as an emotional correlate [61–63] and (c) the adaptive personal and social effects generated by both emotional phenomena [64, 65].

Although happiness can be considered a social phenomenon, whose conditions to experience it involve the perceived quality of relationships with others and the internalization of social parameters about its characteristics [66], it cannot be ignored that it is also an individual and complex emotional state of positive valence, which evolved *Contagious Laughter as an Innate Acoustic Stimulus That Provokes Positive Emotions... DOI: http://dx.doi.org/10.5772/intechopen.108336*

from simpler phylogenetic expressions. The approach to its phylogenetic origins can enrich the contemporary understanding of it. It is precisely its phylogenetic roots that allow establishing a possible connection with contagious laughter.

Both happiness and contagious laughter would have as their common evolutionary basis the innate tendency of human beings to experience positive affect by default [59], which would be related to tendencies to approach situations that require interaction and cooperation with peers, important for the achievement of survival and reproductive success. Given that evolution generally gives rise to new structures, tendencies, or mechanisms based on existing ones [60], it is very likely that happiness and contagious laughter have developed from the default positive mood, representing expressions of greater intensity and complexity.

From what has been said in previous paragraphs, it is clear that both contagious laughter and the laughter caused by it are accompanied by positive emotions, that is, they are emotional laughters. On the other hand, happiness has been considered as a positive emotional state that is accompanied by positive emotions [61]; in fact, some authors consider that happiness implies frequent experience of positive emotions (e.g., [62]). One of the most important emotions that accompany happiness is joy, which due to its basic and ancestral origin can be considered as the precursor of this positive emotional state: joy and its expression through laughter characterized the pleasant social situations of primitive human and nonhuman species [63]; its ancestral roots and its presence in species phylogenetically related to the human being show the interspecific continuity of positive emotions and their emotional expressions and confirm their innate nature.

Both happiness and contagious laughter generate positive effects for those who experience them and for those who interact with them. Some research has shown that both positive emotional laughter and happiness function as protective factors for physical and mental health [64], which can counteract the negative effects of stress. At the social level, the role of contagious laughter was previously discussed as a factor that promotes group cohesion and cooperation [10], likewise, it is considered that there is a high and complex positive relationship between happiness and social behavior [65].

### **6. Conclusions**

Since there are different types of laughter with different origins and natures, in this chapter it was considered important to address the specific nature of contagious laughter, for which the objective was to offer empirical evidence and arguments to demonstrate that contagious laughter and the laughter caused by it have an innate origin.

In the development of the text, it was pointed out that this type of laughter is shared by human and nonhuman primates [26] and that in humans it appears in the early stages of development [27]. Indirect support was offered throughout the chapter for Provine's [1] hypothesis that there is a receptor mechanism for the particular acoustic attributes of this laugh that elicit its distinctive perception and laugh/smile behaviors in receptors; and directly, the ability of this vocalization to provoke positive emotions and affects was verified. The findings of the investigations reported in this text would be converging evidence on the innate nature of this laughter since it is assumed that only stimuli with a clear biological significance can provoke such a number of responses in the subjects exposed to them [67], who would be innately prepared to react to them.

As indicated or suggested in previous paragraphs, the evidence supporting the innate nature of contagious laughter offers additional support to other theoretical perspectives that migth explain the characteristics and scope of this vocalization: (a) ethological perspective, which allows understanding the innate, automatic, reciprocal and relatively invariant relationship between contagious laughter and laughter/smile caused by it; thus, from this perspective, the contagious laughter-provoked laughter relationship could be considered as a typical behavioral sequence of the species [4]; (b) emotional contagion through vocalizations, which is at an early stage of research [68], may also benefit from the evidence presented in this chapter, as it points to the various effects produced by the contagion of exclusively acoustic laugh stimuli; (c) in the controversy sustained by theorists about the function of the acoustic variability of laughter, namely: if it encodes and transmits the emotion of its sender [69] or if the principle function of this is to induce positive emotions or affects in the listeners [70], it is clear that the results reported in this chapter support the second position.

Since contagious laughter possesses distinctive acoustic and perceptual characteristics, generates particular emotional and affective effects and probably has an innate nature, it is likely that this laughter is a distinct vocalization from the other types of laughter already classified and therefore would have different brain correlates of production and perception, evolutionary trajectory and adaptive functions than other types of laughter [10].

Although the reported evidence was based on psychological research, the observed results have anthropological implications: Based on the results reported in this chapter and the relationship that has been established between contagious laughter and the subject of happiness, it can be concluded that human beings are endowed with innate tendencies of perception and expression of a positive emotional nature, which have been important not only for adaptation to the environment but for the construction of cultures and human groups. However, there is still much to investigate on these trends, which merits a multidisciplinary investigation on the subject.
