**4. Capacity of contagious laughter stimuli to provoke positive effects in the listeners**

In previous paragraphs, it has become clear that contagious laughter induces changes in behaviors, vocalizations, and emotions of listeners. At this point, it is intended to report evidence that this type of laughter also induces changes in the effects of the receptors of this vocalization. Within the affective phenomena, affect is related to the assessment or evaluation that a person makes of the stimuli, people, or situations that he/she faces on a daily basis [44]. Given the close relationship between the evaluation of stimuli and the affection generated, the evaluative changes that a person makes of a stimulus associated with contagious laughter stimuli would prove that they have the ability to influence the effects of the people exposed to them.

One of the ways to determine evaluative changes is attitudes, understood as the psychological tendency to evaluate entities, things or people in terms of likes or dislikes, favorability or disfavor [45] and an appropriate way to determine attitudinal changes is through classical conditioning of attitudes (CCA), which allows the formation, intensification or changes of attitudes through the simultaneous presentation of attitudinal objects with stimuli capable of transferring their affective valence [46]. The CCA paradigm involves repeatedly pairing an originally neutral stimulus (which will later be called a conditioned stimulus, CS) with a stimulus with a strong innate affective valence (unconditioned stimulus, US), as a result of this process a change in the valence of the CS will be observed, which will acquire or intensify the positive or negative affective valence of the US [47].

In this order of ideas, the experiment by Arévalo-Pachón and Cruz [48], selected as unconditioned stimuli the most contagious male and female laughter from the study by Arévalo-Pachón and Cruz [29] and as neutral stimuli 2 commercial brands not known in our environment (XUe and XUo) (The neutrality of these brands was empirically established in the study by Noguera [49]), which had the same size, composition colors, and background color.

The study used a within-subject experimental design with measurements before and after the conditioning process. In this experiment, the independent variable was the type of laugh stimulus (laughter more or less contagious feminine and masculine) and the dependent variable was explicit attitudes (they are conscious attitudes susceptible to being reported), measured using semantic differential scales with continuous scales of values between 0 (lowest value) and 6 (highest value), with the following poles: not at all pleasant (0) – very pleasant (6); not at all attractive (0) very attractive (6); not at all shocking (0) - very shocking (6); not at all interesting (0) - very interesting (6) and not at all satisfactory (0) - very satisfactory (6). For this experiment, a convenience sample of 60 participants was taken (the sample size was calculated using the GPower software, version 3.1.9.2 for a repeated measures ANOVA). The participants were university students aged between 18 and 30 years with normal or corrected vision and hearing conditions. The experiment was applied in the biofeedback laboratory of the Universidad de Los Andes.

In this study, the following hypothesis was formulated: after the process of pairing the neutral commercial brands with the more contagious laughter stimuli, the study participants will present explicit positive or more positive attitudes toward these brands than before this pairing.

The application of the research involved three phases: (a) preconditioning: in this phase, the experiment was designed in the OpenSesame Program (version 3.2.7 of 2018) and the semantic differential scales were constructed; at the beginning of the experiment, the subjects were exposed to the different laugh stimuli to collect baseline data on the semantic differential scales; (b) conditioning: the experiment was applied using OpenSesame, which performed the procedure of simultaneous classical conditioning of attitudes in a standardized and controlled way: 5 pairing tests of the commercial brands XUo and XUe were applied with the most contagious feminine and masculine laughter stimuli, respectively; (c) postconditioning: using the same semantic differential scales used in the baseline, but presented randomly, post-test measures of attitudes toward the various commercial brands were taken. The data that allowed verifying the hypothesis indicated above are reported below.

**Table 3** indicates that all the postconditioning attitudinal rating means of the brands paired with the XUo brand are higher than those recorded at baseline. Significant difference between pre/post means was observed in three of these.

*Contagious Laughter as an Innate Acoustic Stimulus That Provokes Positive Emotions... DOI: http://dx.doi.org/10.5772/intechopen.108336*


### **Table 3.**

*Statistical significance of the pre/postconditioning means difference of the semantic differential scales in the rating of the XUo brand using the Wilxocon test (N = 60).*


### **Table 4.**

*Statistical significance of the pre/postconditioning means the difference of the semantic differential scales in the rating of the XUe brand using the Wilxocon test (N = 60).*


### **Table 5.**

*Statistical significance of the pre/postconditioning mean difference in ratings of all the scales of the semantic differential for the XUo and XUe brands using the Wilxocon test (N = 60).*

**Table 4** shows postconditioning means greater than preconditioning in all semantic differential scales paired to the XUe brand and significant differences between pre/post means in 4 of them.

**Table 5** indicates significant differences between the pre and postconditioning means when the scores of all the semantic differential scales are taken into account for the XUo and Xue brands, which confirms the significance of most of the pre/postconditioning differences when taking each of these scales individually.

Based on the data in **Tables 3**–**5** it can be stated that the classical conditioning of attitudes that used the most contagious laugh stimuli generated an attitudinal change in the participants in relation to the values observed at baseline. These results confirm the hypothesis formulated in this research and therefore it can be stated that this type of laughter is capable of influencing the effects of listeners.

These results support the findings of other research that indicate that laughter is processed as an affectively charged stimulus [50] that has the capacity to induce positive effects in listeners [6]. In fact, some authors consider that the main function of any laughter is to induce or intensify positive affect in listeners [51, 52] and that laughter with certain acoustic characteristics can influence and shape the effects of its receptors [51]. On the other hand, the results of the research by Arévalo-Pachón and Cruz [48] are in line with the results of the research by Smoski and Bachorowski [52], which showed that the most laugh-provoking laughs are the ones that most are associated with the induction of positive affect in other people.

The evidence from this study on the ability of the most contagious laugh to transfer positive effects to neutral stimuli contributes to supporting the thesis of the innate nature of this laughter and the effects it produces: human beings would be genetically prepared to respond vocally, emotionally and effectively when they hear other people's contagious laughter [53].

Given the possibility that contagious laughter has phylogenetic antecedents in nonhuman primate species [54] and the observed correlation between the activation of audio motor circuits (such as those that would be involved in contagious laughter) and affective changes in nonhuman primates [12], it could be thought that this laughter has evolved and that throughout its phylogenetic history, the induction of positive emotions and affects in congeners caused by this vocalization would have helped ancestral man to face problems of survival and formation and strengthening of human groups [1, 55].

Effective classical conditioning procedures require the use of US with biological significance, which means that they naturally provoke physiological, affective or emotional reactions of sufficient intensity, capable of being transferred to neutral stimuli [56]; in other words, suitable and reliable US must be part of the repertoire of innate reactions of the species. In this order of ideas, the effectiveness of the most contagious laughter as the US that was observed in this research would support the thesis of its innate nature.
