The model of motivated attention and affective states (which will be herein referred to as the ‘motivational model’) was developed by Lang and colleagues (Bradley & Lang, 2000; Hamm, Schupp, & Weike, 2003; Lang,
1995; Lang, Bradley, & Cuthbert, 1990; Lang, Bradley, & Cuthbert, 1997) and is theoretically founded on the important evolutionally connection between the emotion processing system and primal approach and avoidance systems. The motivational model is concerned with the perception of emotionally distinct stimuli and posits a biphasic perspective, in that stimulus dimensions of valence and arousal elicit activation in underlying appetitive and aversive systems (Lang, et al., 1997). That is, pleasant states promote approach responses driven by the appetitive system while unpleasant states promote withdrawal responses driven by the aversive system, and arousal reflects the level of activation within either system (see Figure 1; Lang et al., 1990; Lang et al., 1992; Lang et al., 1997).
The motivational model is most applicable to research exploring primary emotional responses. Primary emotions have an inherent association with the underlying approach and withdrawal motivational systems, whereas secondary emotions surface in response to the perception and experience of a primary emotional event (Damasio, 1995; Deigh, 2014). More specifically, primary emotions are seen to be implicated in the activation of underlying drive states, or the processes involved in managing preservative (e.g., sexual and hunger drives) and protective (e.g., fear drive) functions (Bradley, 2000; Konorski, 1967; Lang & Bradley, 2010). Similar to the appetitive and aversive systems, primary reinforcements influence drive states in that successful fulfilment of drive states activates the reward receptors in the brain (e.g., mesolimbic system) while the unsuccessful fulfilment of drive states activates the punishment centres (e.g., periventricular system) (Bradley; Konorski; Lang & Bradley). Drive states are thus argued to parallel underlying motivational
systems and can effectively elicit approach and withdrawal behaviours. While drive states are seen to reflect only physiological processes, the subjective feelings that are associated with particular drives and anti-drives (i.e., the feeling of contentment and satisfaction experienced following drive fulfilment) are what constitutes emotions (Bradley; Izard, 2007).
Figure 1. Visual illustration of the motivational model.
Note. The motivational model proposes that responses are larger to emotional (pleasant or unpleasant) relative to neutral stimuli, with greater reactivity to highly arousing relative to low arousing stimuli (comparable activation strength in appetitive and aversive systems).For cues: The apex of the triangle represents low arousing cues and the base of the triangle represents high arousing cues. The width of the triangle represents the level of cue arousal. For system activation: The apex of the triangle represents low system activation while the base of the triangle represents high system activation. The width of the triangle represents the level of system activation.
As theorised by Lang and colleagues (e.g., Bradley & Lang, 2000; Hamm et al., 2003; Lang, 1995; Lang et al., 1990; Lang et al., 1997; Lang & Bradley, 2010), emotions can be seen as ‘action dispositions’ whereby
emotionally laden cues may lead to increased levels of attention and autonomic nervous system activation as an individual prepares to respond to the emotion inducing cue. These increases in attention and reactivity may be the result of either implicit or explicit emotion processing. Implicit emotion processing is automatic, unconscious, fast, and cognitively undemanding while explicit emotional processing is conscious, slow, and cognitively demanding. More specifically, implicit processing is evoked automaticallyby a stimulus and the stimulus is processed without monitoring and without insightand awareness of the occurring processing. In contrast, explicit processing requires conscious effort for initiation, demands some level of monitoringduring processing, and is associated with some level of insightand awareness (Cohen, Moyal,
Lichtenstein-Vidne, & Henik, 2016; Gyurak, Gross, & Etkin, 2011; Salmela, 2014). For example, implicit emotional processing is employed when
participants are required to process a non-emotional attribute of a stimulus such as specifying whether a presented emotional face is female or male whereas explicit emotion processing is demonstrated when a participant is required to identify whether a stimulus is neutral, pleasant, or unpleasant during an emotion categorisation task (Cohen et al.; Gyurak et al.; Salmela). It is important to note that humans possess the ability to reduce or inhibit overt emotional responses following both implicit and explicit processing, even for uncontrollable covert emotional reactions through the process of emotion regulation (emotion regulation was investigated in Study 3). That is, emotions
can be conceived as dispositions towards behavioural action as the body physiologically and cognitively prepares an individual for an emotional response despite the possibility that an overt response may be inhibited or not required.
In summary, the motivational model emphasises key roles of valence and arousal factors in emotion processing which map onto motivational drive states. Specifically, pleasant stimuli stimulate the appetitive system and promote approach behaviours whereas unpleasant stimuli activate the aversive system and promote withdrawal behaviours. In addition to stimuli valence, arousal is the second important dimension which influences the processing of emotional stimuli. Arousal extends from very low levels of arousal to very high levels of arousal and reflects the activation strength of the appetitive and aversive systems when processing emotional stimuli. Extreme arousal states (i.e., very low or very high) can exist within either valence (pleasant or
unpleasant), and arousal level is increased at each end of the valence spectrum. The motivational model thus predicts increased reactivity to pleasant and unpleasant stimuli in comparison to neutral stimuli, with highly arousing pleasant or unpleasant stimuli evoking greater reactivity relative to low arousing stimuli (Bradley, Codispoti, Cuthbert, & Lang, 2001; Lang, 1995; Lang et al., 1990; Lang, Bradley, & Cuthbert, 1992; Lang et al., 1997; Lang & Bradley, 2010).
2.1.1.1. Motivational Model: Behavioural and Physiological Evidence
The fundamental prediction of the motivational model is that pleasant and unpleasant stimuli elicit greater reactivity compared to neutral stimuli,
with highly arousing pleasant or unpleasant stimuli eliciting increased reactivity relative to low arousing stimuli (Bradley et al., 2001; Lang, 1995; Lang et al., 1990; Lang et al., 1992; Lang et al., 1997; Lang & Bradley, 2010). In line with the model predictions, previous research has demonstrated that behavioural ratings of valence and arousal (i.e., pleasantness to unpleasantness; low to high arousing), heart rate, skin conductance response (SCR), startle reflex, and facial muscle activity (electromyography; EMG) are increased to pleasant and unpleasant stimuli compared with neutral stimuli, with greater reactivity to high- relative to low- arousing stimuli (Bradley, 2000; Bradley & Lang, 2000; Hamm et al., 2003; Lang et al., 1997; Lithari et al., 2010; Bernat, Patrick, Benning, & Tellegen, 2006). Further, pleasant and unpleasant stimuli relative to neutral stimuli are viewed for longer durations even when equal visual attention is directed to emotional and neutral stimuli (Bradley & Lang; Bradley et al.; Calvo & Lang, 2004; Lang & Bradley), and even under
conditions where participants are instructed to focus on neutral stimuli (e.g., Nummenmaa et al., 2006). Providing additional support for the motivational model hypothesis, emotional relative to neutral stimuli require greater cortical processing (even when stimuli are unattended), have been shown to capture and hold attention, and have a greater likelihood of being recalled from memory (Buchanan & Adolphs, 2002; Schupp et al., 2007; Vuilleumier & Huang, 2009).
2.1.1.2. Motivational Model: Neuroimaging Evidence
Emotions are thought to be related to activity in brain areas that focus our attention, motivate our behaviour, and influence the significance of the stimuli and events we are exposed to. Emotion has been found to be related to
a group of structures in the center of the brain called the limbic system. Research has shown that limbic structures are directly related to emotion, but non-limbic structures have also been shown to relevant to emotion (Dalgleish, 2004).
The primary structures of the limbic system include the amygdala, hypothalamus, cingulate cortex, and hippocampi (in addition to other structures). The amygdala is involved in detecting and indicating if external stimuli are important and are emotionally significant, and is particularly active when a stimulus is novel or evokes uncertainty, particularly for unpleasant emotions such as fear (Ledoux, 1995; Lindquist, Wager, Kober, Bliss-Morea, & Barrett, 2012). Research has shown enhanced amygdala activation during the perception of threat, with the amygdala accessing past memories to improve judgement of the possible threat (Breiter et al., 1996). Relatedly, the hippocampus allows memories to be stored long term and retrieves them when necessary, with such retrieval used within the amygdala to assist the evaluation of current emotional stimuli (Fischer et al., 2002; Lindquist et al., 2012).
Previous neuroimaging research has established a connection between visual processing regions (e.g., occipital cortex) and the amygdala, with
amygdala reafferents thought to be involved in the early processing of stimuli in the visual cortex (de Kloet et al., 2005). A growing body of neuroimaging evidence indicates that the amygdala is primarily activated during the processing visual stimuli (relative to other sensory stimuli; Boubela et al., 2015; Phan et al., 2002) and salient stimuli (Davis & Whalen, 2001;
Edminston et al., 2013; Liberzon et al., 2003). In addition, the amygdala has been found to be most activated when processing emotional stimuli
(Costafreda et al., 2008; Stevens & Hamann, 2012), although research demonstrating amygdala activation to neutral stimuli if it is salient and important to a task has also been reported (Cooney et al., 2006; Davis & Whalen, 2001; Fusar-Poli et al., 2009; Schwartz et al., 2003). In addition, the hypothalamus has been reported to be involved in reward circuits and in producing physical emotion output (Armony & Vuilleumier, 2013) whereas the cingulate cortex is seen to be important to conscious, subjective emotional awareness (Medford & Critchley, 2010).
Various other brain structures have been associated to emotion. For example, the prefrontal cortex is seen to have a critical role in the regulation of emotion and behaviour by anticipating the consequences of our actions
(Davidson & Sutton, 1995)whereas the orbitofrontal cortex is a structure involved in decision making and the influence by emotion on that decision (Bechara, Damasio, & Damasio, 2000). The ventral striatum is a group of subcortical structures thought to play an important role in emotion and behaviour, including in the experience pleasure (Kringelbach & Berridge, 2016). Further, the insular cortex is thought to play a critical role in the bodily experience of emotion as it is connected to other brain structures that regulate the body’s autonomic functions (heart rate, breathing) and the insula related to empathy and awareness of emotion (Gu et al., 2013; Lindquist et al., 2012).
Extensive research using fMRI methodology has demonstrated that emotional (pleasant and unpleasant) stimuli elicit greater activation compared to neutral stimuli in the visual cortical region, with enhanced activity in
response to high- relative to low- arousing emotional stimuli (Aldhafeeri et al., 2012; Bernat et al. 2006; Bradley et al., 2003; Cuthbert et al. 2000; Hofstetter,
Achaibou, & Vuilleumier, 2012; Lane, Chua, & Dolan, 1999; Lang et al., 1998; Lang & Bradley, 2010). Neuroimaging evidence generally supports the predictions of the motivational model, although divergent evidence which demonstrates that both valence and arousal dimensions contribute to increased activation in the visual cortical areas has also been reported (e.g., Mourão- Miranda et al., 2003).