Title : Individual differences in preference for curvature

People tend to prefer objects with curved contours to objects with sharp contours (Bar & Neta, 2006; Palumbo & Bertamini, 2016). Nevertheless, as with other aesthetic features (Jacobsen, 2004), there are also considerable differences among people in the extent to which they prefer curvature. The aim of the research presented here was to explore the possible reasons for such differences. Specifically, we sought to determine whether individual differences in preference for curvature were explained by participants’ interest in art, studies, openness to experience, intelligence or sex. Thus, we asked 42 participants to perform a 2AFC preference for curvature task (Munar, Gómez-Puerto, Call & Nadal, 2015), answer questions of a Visual Art Interest and Education Scale (VAIES), answer the openness to experience scale from the NEO-PI-R (Costa & McCrae, 1992), and Raven’s intelligence test. Linear mixed effects modeling was used to predict participants’ preference for curvature using their experience with art, openness to experience, intelligence scores, studies, and sex as predictors. We found that openness to experience had a significant negative effect on the probability of choosing the curved alternative and that the probability of choosing the curved alternative was higher for women than for men. The effect of openness is weaker for art students than for others. There were no significant effects of intelligence. These results are discussed in terms of the multiplicity of cognitive and affective processes contributing to aesthetic appreciation (Leder & Nadal, 2014). Keywords: preference, curvature, angularity, empirical aesthetics, individual differences. INDIVIDUAL DIFFERENCES IN PREFERENCE FOR CURVATURE ! 2 Individual differences in preference for curvature Record hypotheses related to art and aesthetics began with the work of Fechner (1876). It is usually considered that this work opened the field of empirical aesthetics, the second, after psychophysics, in experimental psychology (Carreras, 1998; Marty, 1997). Specifically, Fechner began to apply the experimental method to issues related to art, and to recorded the reactions of a sample of subjects taken as representative of the population. In his book Vorschule der Ästhetik (1876), he presented the results of several experiments conducted in laboratory and field experiments. Fechner defined experimental aesthetics as an aesthetics from below, which was based on particular facts and gradually, progressed to create generalizations. The vision of Fechner of aesthetic experience was markedly formalistic, while his interest was to understand the way in which certain formal aspects -especially the proportions governing relations between elementsinfluence the aesthetic appreciation of people. This formalistic perspective had, and still has, an enormous influence on the experimental investigation of the aesthetic phenomenon, while many of the studies continued, and continue, wanting to understand the impact on the aesthetic appreciation of factors such as regularity, symmetry, complexity, color, aspect lines, etc. (Nadal, Gomila, Galvez-Pol, 2014). In addition to laying the conceptual foundations of experimental aesthetics, Fechner also developed three methods that are still used today. The first is the method of choice. It involves asking participants to choose a value to communicate how nice, lovely, or attractive, etc., are different objects. The second is the method of production, by which participants create an object that in their view is nice, beautiful, attractive, etc. And the third method is to examine works of art or other objects, looking for the features that are most frequently INDIVIDUAL DIFFERENCES IN PREFERENCE FOR CURVATURE ! 3 preferred by the society that created them. The method of choice is still the most commonly used today, but is carried out in different ways. The participants are asked to sort the objects according to the preference they have for them, or they are presented with objects in pairs and have to pick one, or subjects are asked to rate numerically the degree of preference for each object. During the first half of the twentieth century, the methodology that Fechner opened for the study of experimental aesthetics, was harshly criticized and accused of being too empirical, quantitative, deterministic and reductionist. Many philosophers often pointed out, that cultural and historical factors that can influence the aesthetic preference, were totally ignored by Fechner’s proposal. Later, Daniel Berlyne developed a comprehensive research program known as psychobiological aesthetics, which became the origin of contemporary experimental aesthetics. Berlyne's main objective was to understand how motivational principles influence aesthetic preference. Based on neurobiological discoveries of his time on the motivational and emotional systems, Berlyne (1971) argued that there are three neural systems whose activity induces motivational state of an organism. The first system is rewarding, the second is aversion, and the third is inhibition of aversion. The activity of the three systems, according to Berlyne, depends on the degree of excitation of the body, which in turn depends on the configuration of the stimulus. He proposed the term "hedonic tone" to explain the ability of the stimulus to generate a reward response of pleasure or preference in the subject, causing it to emit linguistic statements. For Berlyne, not only the intrinsic formal properties of the object, as claimed by Fechner, create aesthetic experience. For him, it is the way in which the observer perceives the object, that organizes and generates aesthetic experience. Thus, Berlyne went beyond the strictly formal view of Fechner, and recognised the active role of the observer. Berlyne argued INDIVIDUAL DIFFERENCES IN PREFERENCE FOR CURVATURE ! 4 that a full understanding of human aesthetic experience can only emerge from multidisciplinary work of psychological approaches, neuroscientists and evolutionists. But advances in neuroscience and psychology, showed that the proposal of Berlyne was too simple and limited, which left experimental aesthetics without a general theoretical framework until the proposals of Leder et al. (2004) and Chatterjee (2004) that gave meaning to the discoveries and advances, psychological and neuropsychological, produced in previous decades. Leder et al. (2004) published a model of aesthetic experience conceived as a result of a complex interaction of cognitive and affective processes. The model is divided into five stages of information processing of the aesthetic experience. All of them are connected in sequence. The flow of information is one way in some parts of the model, and other bidirectional, which means that some stages contain bottom-up processing but also top-down. Also it works in parallel, an affective evaluation system on the output arising from the stages of information processing of aesthetic experience. The model of Leder et al. (2004) explains that when a visual stimulus is presented to the subject, specific stimulus features are extracted in each of the five stages of information processing. In the first phase, perceptual analysis, where properties such as complexity or symmetry are detected, occurs. The second phase involves memory integration, where the perceptual information relates to past experiences. The third phase, involves explicit classification, where the art experience of the observer comes into play, affecting the processing of information. In the fourth phase a meaning, or interpretation, is assigned to the stimulus. At that time, we know what we see. The fifth phase is the evaluation phase, which results in an aesthetic judgment and an aesthetic positive or negative emotion, about the work of art. In their model, Leder et al. (2004) specify that there are certain visual properties that can potentially affect the aesthetic preferences, since it has been found that people's INDIVIDUAL DIFFERENCES IN PREFERENCE FOR CURVATURE ! 5 preference for objects is influenced by certain visual properties. Contrast (Ramachandran & Hirstein, 1999), complexity (Berlyne, 1970, 1974; Frith & Nias, 1974), symmetry (Julesz, 1971), color (Martindale & Moore, 1998), and grouping (Marr, 1982), have been some of the visual properties that have been taken into account to study aesthetic preference during the 1990s. But in the last decade, preference for curvature has also received attention from researchers. Lundholm (1921), was the first to show that the angular lines were perceived as angry, serious and difficult, while curved lines were associated with what it is calm, sad, gentle and kind. That is, Lundholm (1921) conducted the first experiment that showed that humans experience differently curved and angular lines. Subsequently, Poffenberger and Barrows (1924) corroborated Lundholm’s experiment with the same results: curved lines and forms were considered more harmonious, pleasant and relaxing (Gómez-Puerto, Munar, Nadal, 2016). But Bertamini et al. (2015) clarified that the curved lines are not only associated with positive terms such as "friendly" or "relaxed", but also with negative, as "sad" or "lazy". Bertamini et al. (2015) also found that the angular lines are considered more complex than curved. Uher (1991) studied the relationship between the zigzag lines in different cultures, and found that they were associated with adjectives of fighting, while curved lines were associated with adjectives of kindness (Gómez-Puerto, Munar, Nadal, 2016). Larson et al. (2007), once again showed that people associate geometric forms V-shaped, or angled, with the feeling of anger, while the curved, are associated with happiness. Contour curvature is preferred in broad range of visual stimuli: people prefer objects (Bar & Neta, 2006), rooms (Vartanian et al., 2013), designs (Westerman et al., 2012), and geometric figures (Silvia & Barona, 2009; Palumb