Emotions

Emotions are defined as “an episode of interrelated, synchronized changes in the states of all or most of the five organismic subsystems in response to the evaluation of an external or internal stimulus event, as relevant to major concerns of the organism” (Scherer, 2001). This definition implies that emotions are triggered by stimulus events which are relevant for our well- being. According to this view, stimuli are evaluated according to several appraisal dimensions resulting in a response synchronization (Scherer, 2001), which permits organism to cope adaptively with environmental events by the mobilization of resources. The sequence of

appraisals changes rapidly due to new information and re-evaluation, allowing fast readjustments to changing situations. Emotional response patterns are assumed to be of high intensity and short-lived, so that resources remain available to behave flexibly when facing future environmental stimuli.

So that emotional responses are useful to face environmental demands, organisms must have an efficient perceptual system to detect emotional stimuli. Focusing on fear, it is very important to efficiently locate threat-related stimuli so that defensive behaviors can be quickly triggered. It is of note that from an evolutionary point of view, failing to detect a potentially harmful stimulus and its appropriate response is more costly than eliciting a defensive reaction to a harmless stimulus. In other term, it is preferable to be too cautious, which makes it probable that our perceptual system is biased toward identifying threat in the surroundings.

1.11.1. Fear

Fear is an emotional state which motivates avoidance behavior when facing danger (Gallagher & Holland, 1994). It has been described as being highly relevant for one’s current goals and associated with very low coping potential (Scherer, 2001), leading to behavior characterized by inhibition or avoidance (Frijda, Kuipers, & Ter Schure, 1989). This idea is based on the emotion system theory by Gray (1994). This model posits that individuals have a behavioral approach system (BAS) and a behavioral inhibition system (BIS) which can be more or less dominant depending on the kind of behavior involved by the emotion. Corroborating this idea, Davidson and Hugdahl (1995) demonstrated that anxiety/fear is linked with dominance of the inhibition system (BIS). Moreover, fear has been classified as one of the “basic emotions”, because of its biological and social functions (Plutchik, 1980). Öhman and Mineka (2001) have suggested an evolved fear module, which is a neural system highly sensitive to evolutionary relevant threat stimuli, allowing their fast detection and adaptive behavior. This idea suggests that we are more likely to fear events and stimuli, which were threatening for the survival of our ancestors such as spiders or snakes rather than dead objects, such as weapons or motorcycles (Marks, 1962). Data have shown that fear can be elicited by these threatening stimuli, even when they were rendered

less visible by a masking procedure, supporting the fear module hypothesis (Öhman & Soares, 1994).

At a neurological level, LeDoux (1996) posited a system to explain the high ability of organisms to detect and show adaptive response to threatening stimuli. In his model, he proposed a direct neural link between the thalamus and the “significance evaluator” and “fear effector system” located in the amygdala. This monosynaptic link bypasses the traditional thalamo-cortical sensory pathway, to allow a faster detection of emotional stimuli. LeDoux (1996) qualified this route as “quick and dirty”. The first point to test LeDoux’ model (1996) is that fear stimuli should activate the amygdala, even if they are not consciously identified by the perceiver. Presentations of pictures specific to participants’ phobia showed bilateral activation of the amygdala when phobic pictures, namely snakes for snake-phobics and spiders for spider-phobics, but not for fear-relevant but non phobic pictures (Carlsson et al., 2004). Moreover, it is of note that amygdala activation has been found even when fear stimuli were rendered less visible by a backward masking procedure. In order to find more conclusive evidence regarding the monosynaptic link between thalamus and amygdala, Morris, Öhman, and Dolan (1999) examined the connectivity between these regions. They found that amygdala activation by masked stimuli could be predicted by the activation of the superior colliculus and the right pulvinar nucleus located in the thalamus, supporting LeDoux’s hypothesis (1996).

1.11.2. Fear and anxiety

Anxiety and fear are both aversive affective states focused on a threat. They both imply intense negative feelings and somatic changes. Despite this similarity, the question regarding the overlap between fear and anxiety is still debated. Some authors suggest that they form a single personality dimension in the population (Eysenck, 1967), whereas in the clinical population they can be dissociated (e.g., Wolpe & Lang, 1977). Authors tried to decipher this discrepancy between anxiety and fear conceptualization. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR; American Psychiatric Association [APA], 2000) anxiety is defined as an

”apprehensive anticipation of future danger or misfortune accompanied by a feeling of dysphoria or somatic symptoms of tension” (p. 820). According to this definition, we can distinct both

concepts regarding the fact that fear must be triggered by an identifiable stimulus. From that point of view, anxiety is an anticipatory response to more or less threatening stimuli, whereas fear is a response to identifiable fear stimuli. Another distinction comes from Epstein (1972), who argued that fear is associated with coping behavior, more precisely flight and avoidance responses, whereas fear turns into anxiety when no control over the situation is possible. In sum, Epstein views fear as a “motivation to escape” and anxiety as a “a state of undirected arousal following the perception of threat”. He also mentioned that in the case of fear, the eliciting stimulus is quite clear, which is not the case for anxiety, whose threatening stimulus is assumed to be more fuzzy, making action to cope with defensive behavior more difficult. Finally, Gray and McNaughton (2000) suggested that anxiety is elicited when a threatening stimulus must be approached whereas fear, which is characterize by a flight response if such behavior is available in the situation, is elicited by threatening stimuli which can be avoided. Therefore, the two draw upon distinction different emotional and motivational states according to the possible behaviors used to cope with the threat.

At the neurological level, anxiety and fear share common neural mechanisms but at the same time activate distinct specific brain areas. On the one hand, it has been suggested that the central nucleus of the amygdala is activated during fear responses to clear eliciting stimuli whereas the bed nucleus of the stria terminalis is activated during anxiety, which is a longer state, without a distinct eliciting stimulus (Davis, 1998; Davis & Shi, 1999). On the other hand, these structures are related to the same parts of the hypothalamus and the brainstem that influence fear and anxiety, illustrating the large overlap between fear and anxiety responses.

1.11.3. Implicit fear stimuli

Very little is known about the impact of implicit fear on judgments and behavior. Öhman and Soares (1994) used the term “unconscious anxiety” in their paradigm. However, the term

"unconscious anxiety” had nothing to do with an eventual “unconscious” emotional reaction, when facing the stimulus, but was directly related to the eliciting stimulus himself. In other terms, it referred to the fact that a masked threatening stimulus elicited a conscious fear reaction.

Therefore, these experiments are not directly linked with our conception of implicit fear.

Brosschot, Verkuil, and Thayer (2010) conceptualized “perseverative cognition” as

“repetitive or sustained activation of cognitive representations of past stressful events or feared events in the future” which can be either conscious or unconscious. Their point relies on the fact that it is not stressful events per se, which are responsible for sustained physiological activation, but rather perseverative cognition such as worry and rumination. They even argue that unconscious perseverative cognition is the main determinant of stress-related physiological arousal. This has important implications, because stress has traditionally been studied in paradigms that contained a real stressor. On the contrary, these authors suggested that the mere cognitive representation of stress, which is assumed to be personally relevant, is powerful enough to evoke long-lasting arousal effects.

Other researchers used the term “unconscious fear” in a paradigm in which they investigated the impact of masked emotional faces on an attention response (van Honk, Peper,

& Schutter, 2005). They showed an attentional biased reflecting slower responses when masked fearful faces were displayed in comparison to neutral faces. However, most of the affective priming studies have not used fearful faces in their manipulations. Murphy and Zajonc (1993), Winkielman, Zajonc, and Schwarz (1997) or Winkielman et al. (2005) for instance have used happy versus angry faces to investigate their effects on liking judgment of ideographs. Niedenthal (1990) conducted an experiment in which cartoons were evaluated after being preceded by flashed happy or disgust faces. Zemack-Rugar et al. (2007) used words related to sadness and guilt to study the effect of their activation on behavior. This lack of data regarding the influence of implicit fear on human behavior is surprisingly. We will contribute to close this gab by providing evidence for an impact of implicit fear on effort mobilization.