The Psychological Mechanism Of Facial Expression Detection

Visual awareness refers to the subj ective experience of seeing,as contrasted to unconscious visual processe.Review of previous researches,many researchers studied on the conscious processes.In recent years,researchers have begun to focus on conscious detection gradually,that pre-conscious processe.The experimental materials of previous researches selected simple stimulation,such as gray dots,simple graphics and so on.Facial expressions through the eye muscles,facial muscles and mouth muscles changes to show individual emotional states.As the important tool to show human emotion and cognitive emotion,facial expressions has the vital significance in the human social interactions.Correctly facial expression recognition is an important skill for human survival.So,this study has selected facial expression as experiment material,and studied the psychological mechanism of facial expression detection.In the domain of consciousness,the rendering time of experiment materials is a very important question.How to choose a point in time the stimulation present in the suprathreshold level or subthreshold level,haven't a fixed standard.Study 1 adopted two methods to measure the detection threshold of facial expression,in order to provide data support to the unconscious studies.The principle of signal detection theory was used to measure the detection threshold of facial expression in the experiment 1.Results showed,the threshold of anger was from 33ms to 50ms,and other expressions were from 17ms to 33ms.The highest discrimination ability was happiness and fear,the lowest was the anger.With the rendering time increasing,the discrimination ability of facial expression was growing.The discrimination ability of female is stronger than male's.But limited by the disadvantage of signal detection theory,researchers cannot precisely measure the detection threshold.In the experiment 2,detection thresholds of 6 expressions were measured through the perspective of psychological physics.Results showed,the detection thresholds of happiness,fear,disgust,sadness,surprise and anger were 33.0ms,33.4ms,35.5ms,37.1ms,38.3ms,and 39.4ms.Different facial expressions have different difficulty of discrimination,happiness and fear were easiest,and anger was the most different.The discrimination ability of female was stronger than male.Different subjects have different sensitivities.Based the perspective of gender,age,and trait anxiety level,the study 2 studied the influence factors of facial expression detection.The experiment 1 studied the facial expressions detection with age and gender.Results showed,in all types of emotions,the detection threshold of older adults were greater than the younger' s.The results suggested the ability of facial expressions detection had age difference,the ability of facial expressions detection was recession in older adults.In addition,in the younger group,the detection threshold of anger was greater than the threshold of disgust,fear and happiness,the detection threshold of fear and happiness were less than the threshold of fear and anger,sadness and surprise.In older group,the detection threshold of anger was greater than other expressions,the detection threshold of happiness was less than other expressions.This suggested that,compared with other expressions,the recession of the ability of detect happiness was minimized in older adults;the recession of the ability of detect fear was maximumized in older adults.Finally,this study also found that the detection threshold of female was less than male,which suggested gender difference was exist,the females's ability of facial expression detection was greater than male' s.The experiment 2 studied the relationship between facial expression detection and trait anxiety levels.Experiment results showed that compared with low trait anxiety level of the individuals,the detection threshold of high trait anxiety level individuals was lower,and namely.When detecting other expressions,there was no significant difference in the level of trait anxiety.Reviewing ERP studies on facial expression unconscious processing,the rendering time of supthreshold and subthreshold processing were different,so ERP components of the two conditions can not be compared directly.When unconscious processing and conscious processing were separated,and how the neural mechanisms of separation was,were not researched.The study 3 studied neural mechanisms of facial expression detection by combining with the computer's refresh rate,selecting the time near the threshold of expression detection,and using event-related potential technique based on the study 1.Because the rendering time of experimental materials was near the threshold,the participants sometimes can detect facial expression,sometimes cannot,but rendering time of two processing conditions were same,so ERP components can be directly compared.The results showed that compared with anger,the fear tended to elicit earlier N1 component;compared with anger and fear,the happiness tended to elicit earlier P1 component.Under fear and happiness conditions,conscious condition tended to elicit earlier P2 component than unconscious condition;But under anger condition,the latency of conscious and unconscious were no difference.The amplitude of N2 under the conscious condition is significantly less than under the condition of unconscious;and the amplitude of P3 under the condition of conscious was significantly greater than under the condition of unconscious;the amplitude of P3 caused by happiness was greater than fear and anger's.The amplitude of N3 under the condition of conscious was significantly less than under the condition of unconscious;LPC amplitude under the condition of conscious was significantly greater than under the condition of unconscious.That is to say,the brain was preferred to process fear,followed by happiness,and finally anger.The separation of conscious and unconscious aboutfacial expression occured in 200ms after stimulus presentation,and the separation lasted until the end of processing.Different expressions have different separation times;the separation of anger was later than other expressions.Facial expression detection had three stages,conscious and unconscious of fear and happiness were separated in first stage,conscious and unconscious of all expressions were separated in second stage,conscious processing in third stage.