Attention Bias And Its Processing Mechanism For Motivation - Related Emotional Stimulation

Some stimuli have more direct relevance for our survival and well-being than others. These more relevant stimuli include stimuli that signal danger or threat, such as predators or enemies, as well as stimuli that signal chances for growing and expansion, such as nutritional and energy resources or potential mates. Given the high importance of such emotional stimuli for an individual, the perceptual processing of these stimuli should be prioritized to allow for a rapid appraisal of the situation and consequently the rapid preparation of an appropriate behavioural response. In line with this, extant research demonstrated that delicious foods, cute babies, erotic scenes, but also poisonous snakes, scenes of violence, attack or war and mutilations seem to catch one’s attention more easily and hold one’s attention longer than neutral stimuli. In the literature, the phenomenon that relative to neutral stimuli, attention is preferentially or more allocated to emotional stimuli is referred to as attentional bias. Individuals showing obvious attentional bias to the emotional stimuli listed above may be due to these stimuli are of high relevance to the basic motivational imperatives such as survival and reproduction.Both the motivational theory of emotions and the relevance appraisal theory of emotions state that the motivational relevance of a stimulus has a critical influence on attentional bias. The motivational theory of emotions posits that emotion is fundamentally organized around the appetitive and aversive motivational systems. The goal of such an organization is to promote survival by allowing an individual to detect quickly and to face efficiently any event that is relevant for his survival. This theory proposes that, regardless of stimulus valence, the motivational relevance of an emotional stimulus guides individuals’attentional allocation. The appraisal theory of emotions assumes that there is a general mechanism in which the rapid, multilevel assessment of stimulus relevance for the goals, needs, and well-being of the individual, irrespective of stimulus valence. During evolution, not only threat-related stimuli are preferentially perceived by the human brain, but also all classes of stimuli that have high motivational significance are prioritized by the attention system. In light of the motivational theory of emotions and the relevance appraisal theory of emotions, attentional bias is valence non-specific. That is, individuals’ attention is biased not only to threatening stimuli, but also to stimuli that have relevance for basic motivational imperatives such as survival and reproduction, including foods, babies, sexual stimuli, and so on.Therefore, based on the motivational theory of emotions and the relevance appraisal theory of emotions, the present dissertation conducted four studies using emotional Stroop task, visual search task, dot-probe task and emotional spatial cueing task, to systematically investigate attentional bias to motivational relevant stimuli and the underlying processing mechanisms, including component mechanisms and automatic processing mechanisms.Research has revealed the robustness and universality of attentional bias towards threatening stimuli. But, disproportionately, only a few studies have verified attentional bias towards positive stimuli of motivational significance. Therefore, Research 1 conducted 2 replication experiments to further confirm attentional bias to motivationally significant stimuli of positive valence. Experiment 1, using the dot probe task, revealed that partipitants’ attention is biased towards infant pictures when infant pictures and adult pictures were presented together. Experiment 2, employing the visual search task, showed the food detection advantage in the visual search processes. These results implied that the attentional bias effect is valence non-specific. That is, attention is not only specifically biased to negative or threatening stimuli, but also to motivationally significant stimuli of positive valence.Despite Research 1 verifying that the attentional bias effect is valence non-specific, to date there has been many disputes on which dimension or property is a critical factor in eliciting attentional bias to emotional stimuli. Following the motivational theory of emotions and the relevance appraisal theory of emotions, motivational relevance guides the allocation of attentional resources. Thereby, Research 2 implemented 6 experiments, using the emotional Stroop and dot probe tasks, to explore attentional bias to negative and positive stimuli varying in motivational relevance. Results showed that, irrespective of the emotional valence, participants showed obvious attentional bias towards high motivational relevant stimuli. This attentional bias effect is embodied in the significant emotional Stroop interference and congruency effects. On the contrary, attentional bias to low motivational relevant stimuli is nonsignificant. The results of Research 2 provided support for the motivational theory of emotions and the relevance appraisal theory of emotions.Research 2 confirmed that motivational relevance has a critical influence on attentional bias. Nonetheless, to date there has been little agreement on the component mechanisms of attentional bias. In other words, it is unclear whether attentional bias is resulted from facilitated engagement or delayed disengagement, or both. Thereby, Research 3 employed the visual search, dot probe, and emotional spatial cueing tasks to systematically examine the component mechanisms of attentional bias to motivational relevant stimuli. Results showed the robustness of delayed disengagement from motivational relevant stimuli. The delayed disengagement component is observed in the visual search task with the same target type and different distractor types, the dot probe task, and the emotional spatial cueing tasks. The visual search task with different target types and the same distractor type was sensitive to observe facilitated engagement to motivationally relevant stimuli. In the dot probe task, the facilitated engagement is observed only when the cue exposure time is very short (100 ms). Furthermore,. Research 3 has showed that the exposure time of cuing stimuli modulated the attentional bias effect and component pattern for motivationally relevant emotional stimuli. Specifically, when the exposure time of cuing stimuli was relatively shorter (100 and 250 ms), regardless of the valence of cues, there were similar attentional bias effect and component pattern for motivationally relevant stimuli. However, when the presentation-time of cuing stimuli was relatively longer (1250 ms), the attentional bias effect for. motivationally relevant negative stimuli faded away, whereas the effect is still significant for motivationally relevant positive stimuli. Moreover, the bias effect for motivationally relevant positive stimuli was derived from delayed attentional disengagement.Another issue on the processing mechanisms of attentional bias is whether there is automatic attentional bias under conditions of restricted awareness. The former three studies have confirmed the attentional bias effect for motivationally relevant stimuli under conditions of unrestricted awareness. It is unclear whether normal individuals show automatic attentional bias for motivational relevant emotional stimuli under conditions of restricted awareness. Research 4 employed the subliminal emotional Stroop task, the visual search task with different set size, and the subliminal dot probe task to investigate automatic attentional bias to motivationally relevant emotional stimuli. Results verified the automatic attentional bias effect for motivationally relevant emotional stimuli. In particular, there were significant emotional Stroop interference and congruency effects. The set size of stimulus matrix has no effect on the speed of visual detection for motivationally relevant target among neutral distractor matrix. Further, Research 4 observed automatic facilitated engagement, but no automatic delayed disengagement.In conclusion, the dissertation verified that the attentional bias effect is valence non-specific through conducting 4 studies by employing various experiment paradigms. Motivational relevance has a critical influence on attentional bias towards emotional stimuli. This provided support for the motivational theory of emotions and the relevance appraisal theory of emotions. Research concerning the component mechanisms demonstrated that the delayed disengagement effect is robust, whereas the emergence of facilitated engagement effect required fulfilling some more stringent conditions, such as the visual search task with different target types and the same distractor type or the dot probe task with relatively shorter cue exposure time. Moreover, the dissertation has verified automatic attentional bias to motivationally relevant stimuli and this effect stemmed from automatic facilitated engagement.