1.1 Through the lens of dimensional theories

1.1.1 Spinoza and Wundt’s legacies

Generally, dimensional theories represent a particular affective phenomenon as a set of coordi-nates in a low-dimensional space; thus allowing the differentiation of a wide range of phenomena while acknowledging the infinite richness of emotional experience. Consequently, a major task for dimensional theorists is to define the dimensions that best represent this space. This challenge leads to further questions about the optimal number and the nature of such dimensions. Early dimensional theories often don’t directly address the link between emotion and attention. Yet, attention is often implicitly referred to in the functional description of the orthogonal dimensions proposed by each model. The orienting of attention is thus often accounted for by the common effect of the evaluative systems supporting each dimension.

The idea that the emotion domain can be reduced to a small number of dimensions may have first been introduced by the 18th century Dutch philosopher Baruch Spinoza. According to him, not only are emotions pleasant or unpleasant, but they are also weak or strong, and short-lived or persistent (Osgood, 1957). Wundt (1896) rejuvenated the idea, and proposed to structure the space of feelings2 along three dimensions: pleasure–displeasure, arousal–rest, and tension–

relaxation (Figure 1.1, panel a).

After Wundt, many theorists proposed low-dimensional models to account for the full range of

Figure 1.1: Panel a. The three-dimensional space of feelings (“Gef¨uhle”) proposed by Wundt (1896). Panel b. The circumplex model of affect (Russell, 1980).

emotional experience. Assuming that the meaning of emotional words transcends emotional expe-rience, Schlosberg (1952), Osgood et al. (1975), and Russell & Mehrabian (1977) came to the con-clusion that the emotional domain comprises three orthogonal dimensions: pleasure–displeasure, levels of arousal, and dominance–submissiveness. In other words, they argued not only that emo-tional words can be used to probe the space of emoemo-tional experience, but that this space can also be reduced to a minimal set of three dimensions. Using different sorting and scaling techniques on a selection of 28 emotional words, Russell (1980) concluded that this space could be reduced to a two-dimensional representation along the dimensions of valence and arousal (see also Plutchik, 1962, 1980). This model was very appealing in that it conveniently represented a broad range of emotional phenomenon on a circle, dubbed a circumplex model of affect (Figure 1.1, panel b).

These results were then replicated in a cross-cultural context (Russell, 1983), and extended to the perception of prototypical emotional facial expressions across cultures (Russell et al., 1989).

Russell made two fundamental claims that contributed to establish dimensional models in general, and his two-dimensional circumplex in particular, in the scientific community (Russell, 1980, 2003;

Russell & Feldman Barett, 1999): a) the valence/arousal circumplex is an integrative model that represents the structure of affective experience, and b) it also represents the cognitive structure underlying affect. Some researchers took these claims quite literally, and attempted the description of the functional systems implementing these two dimensions in the nervous system, as we will see in the next section. These fundamental claims have been very appealing to a wide range of disciplines. The conceptual economy obtained from representing emotional constructs in such a two-dimensional space is indeed useful in many respects: In clinical settings, for instance, it eases the diagnostic process (Davidson, 1998); in affective computing (Picard, 1997), where engineers build artifacts that can sense and express emotions, a low-dimensional representation reduces the complexity of the computations.

Recent results however challenge the notion that a minimal two-dimensional space is sufficient to fully represent the emotion domain. In an effort to best fit the semantic space of emotion terms, we3 constructed a novel instrument based on the predictions formulated in the framework of major emotion theories. This instrument comprehensively gathers 144 features, representing the six components explicitly assumed by most emotion theorists as centrally relevant to the domain of emotion. We used this instrument to evaluate the semantic space of 24 prototypical emotion words, in three different Indo-European cultures. We found robust evidence for at least four dimensions, which accounted for 75.5% of the total variance. In order of importance: evaluation–

pleasantness (35.3%), potency–control (22.8%), activation–arousal (11.4%), and unpredictability of the occurring event (6.0%). Whereas the first three dimensions resemble the space suggested half a century ago, the fourth dimension, unpredictability, is not reported by most studies. This latter dimension reflects the urgent reaction to novel stimuli and unfamiliar situations. Of most interest, it renders an explicit continuum differentiating the semantic spaces of surprise, fear, and anxiety.

It is most likely that fear and anxiety share a common evolutionary path. Yet, these are concep-tually different affective phenomena, which differ with respect to the object of attention and the associated behavioural response: When fear is elicited by threatening objects in the vicinity of the organism, often requiring an immediate response, anxiety is often elicited by objects characterised by a looser probability of occurrence, in a more or less distant future. One can easily distinguish the implication of attentional processes in the prediction and perception of forecoming threats, as emphasised in a number of studies addressing the influence of attention in the etiology and maintenance of anxiety disorders (Epstein, 1972; Eysenck, 1992; Wells & Matthews, 1994). This new dimension thus constitutes a fruitful extension of traditional dimensional theories, especially with regards to the link between emotion and other processing systems like attention.

In the family of dimensional theories, one model stands out by formulating possible mechanisms for the interaction of affective phenomenon with other systems, like attention. It is embodied into the concept of core affect (Russell & Feldman Barett, 1999; Russell, 2003). In the next section, we will introduce this conceptualisation, and formulate predictions that can be made about the link between emotion and attention in this theoretical framework.

1.1.2 The “core affect” hypothesis: Attention will be drawn by

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