Conformism and oscillations in vaccination coverage.

<p>The evolution of the number of infected (thin line) and (thick line) vaccinated individuals is depicted. Conformism (illustrated by Model 5) increases the amplitude of oscillations and slows down the rate at which alternative opinions of vaccination alternate. The situation is indicated for infections that are moderately infectious (with a reproductive ratio (R₀) varying from 3 to 5) and with the rate of negative side effects from the vaccination (<i>δ</i>^<i>V</i>) varying from 0.5 to 2.</p

Structure of the behaviour-incidence model.

<p>The model is an augmentation of a classic SIR compartmental model [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142990#pone.0142990.ref030" target="_blank">30</a>]. Individuals are characterized by both their epidemiological status (<i>S</i>: susceptible; <i>I</i>: infected; <i>R</i>^<i>v</i>: recovered through vaccination; <i>R</i>^<i>g</i>: recovered naturally) and for each compartment, their opinion of vaccination (positive: subscript p; non-shaded colours; negative: subscript n; shaded colours). <i>C</i>^<i>V</i> and <i>C</i>^<i>I</i> are compartments that indicate the total recalled number of individuals having suffered negative side effects from vaccination and infection, respectively. <i>β</i> indicates the rate of infection transmission; Ω indicates the rate at which individuals change their opinion (from positive to negative Ω or from negative to positive Ω′); <i>δ</i> indicates the number of individuals suffering side effects from either vaccination <i>δ</i>^<i>V</i> and infection <i>δ</i>^<i>I</i>; <i>θ</i> indicates the rate at which individuals vaccinate. Each individual dies at the same rate <i>d</i>.</p

Confirmation bias, conformism and the emergence of oscillations in vaccination coverage.

<p>The emergence of oscillations (o) is depicted as a function of an infection’s reproductive rate (R₀) and the rate of negative side effects from vaccination (<i>δ</i>^<i>v</i>). The emergence of oscillations is contingent on the inclusion of confirmation bias but not conformism and is observed for intermediate values of R₀. Three models are considered: Model 3 (without either confirmation bias or conformism); Model 4 (including confirmation bias) and Model 5 (including both confirmation bias and conformism). If no oscillations emerge, three dynamics can be noted for the distribution of opinions of vaccination: (i) coexistence of 2 opinions with a greater number of individuals with a positive opinion (+), (ii) coexistence of 2 opinions with a greater number of individuals with a negative opinion (-), (iii) all individuals have a positive opinion (*). The models are analysed for 2 different generation times (birth (<i>b</i>) = death (<i>d</i>) = 1 and 0.5) and for different values of the rate of negative side effects from infection (<i>δ</i>^<i>I</i>). 1 million iterations were run with a time step of 0.0001 which correspond to 100 unit of time.</p

Components of the different nested models.

<p>Components of the different nested models.</p

Infection and opinion dynamics as a function of the reproductive rate of the infection (model 5).

<p>For each value of R₀ (number of secondary infections which can be understood as the fitness of the pathogen; it must be >1 for the pathogen to invade the population), the time-series of the dynamics of the infection (top panel; the thin line corresponds to the number of infected individuals and the thick line corresponds to the number of vaccinated individuals) and opinion (bottom panel; the dashed grey line indicates the number of individuals who have a positive opinion and the dashed black line indicates individuals who have a negative opinion) are depicted for a rate of negative side effects from vaccination <i>δ</i>^<i>v</i> = 0.7. Alternative changes of opinions of vaccination and oscillations in vaccination coverage emerge for intermediate values of R₀. When the reproductive rate of the disease is large (R₀ >4), the negative opinion of vaccination disappears and vaccination coverage, while reaching high levels, does not reach herd immunity. This is because the infection spreads too quickly. More generally, four dynamics can be observed and a₁ to a₃ represent their limits which can be moved depending of the values of <i>δ</i>^<i>v</i> considered.</p

Parameters used and their default values.

<p>UT denotes the unit of time which can be expressed in year or ten years.</p><p>Parameters used and their default values.</p

The raters' choices according to the artificial faces hypotheses in Study 2 (See figure 2). The raters predominantly preferred faces similar to their own.

<p>The raters' choices according to the artificial faces hypotheses in Study 2 (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049791#pone-0049791-g002" target="_blank">figure 2</a>). The raters predominantly preferred faces similar to their own.</p

Example of facial features for the four women appearing in a quartet in Study 2.

<p>The rater’s traits were recorded in the computer program. Then, the four faces of the same virtual woman were presented, depending on the rater’s own traits (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049791#pone-0049791-g002" target="_blank">figure 2</a>). An example for a rater with light eyes, no chin dimple, dark hair, thick eyebrows and thin lips.</p

Men’s Preference for Women’s Facial Features: Testing Homogamy and the Paternity Uncertainty Hypothesis

<div><p>Male mate choice might be based on both absolute and relative strategies. Cues of female attractiveness are thus likely to reflect both fitness and reproductive potential, as well as compatibility with particular male phenotypes. In humans, absolute clues of fertility and indices of favorable developmental stability are generally associated with increased women’s attractiveness. However, why men exhibit variable preferences remains less studied. Male mate choice might be influenced by uncertainty of paternity, a selective factor in species where the survival of the offspring depends on postnatal paternal care. For instance, in humans, a man might prefer a woman with recessive traits, thereby increasing the probability that his paternal traits will be visible in the child and ensuring paternity. Alternatively, attractiveness is hypothesized to be driven by self-resembling features (homogamy), which would reduce outbreeding depression. These hypotheses have been simultaneously evaluated for various facial traits using both real and artificial facial stimuli. The predicted preferences were then compared to realized mate choices using facial pictures from couples with at least 1 child. No evidence was found to support the paternity uncertainty hypothesis, as recessive features were not preferred by male raters. Conversely, preferences for self-resembling mates were found for several facial traits (hair and eye color, chin dimple, and thickness of lips and eyebrows). Moreover, realized homogamy for facial traits was also found in a sample of long-term mates. The advantages of homogamy in evolutionary terms are discussed.</p> </div

A typical screen shot during the evaluation of the women’s facial features by the raters in Study 1.

<p>Women aged 18–25 were recruited and three facial photographs (triptych) were taken. A computer program was used to randomly present drawn pairs of triptychs to male raters. For each pair, the rater had to click on the picture depicting the woman that he found the most attractive. The pictures and information were used with each woman’s consent for publication.</p