Effects Of Different Screen Blue Light Levels On Alertnes

Visible light is the part of the electromagnetic spectrum that human eyes can perceive.Generally,human eyes can perceive electromagnetic waves of 400～760nm.Blue light refers to visible light with a wavelength of 380 ～ 500 nm,which has a short wavelength and high energy.In addition to natural sunlight,blue light is found in the displays of electronic products such as mobile phones and computers,as well as artificial light sources such as CFLS and LED lights.In recent years,with the discovery of intrinsic photosensitive ganglion cells(ip RGCs),people gradually realized that ambient light not only has traditional visual effects,helping people to form visual information such as shape,color and spatial orientation of surrounding objects.It also has non-visual effects,affecting the body’s alertness,emotion and cognitive processing.However,most of the previous studies on the effects of ambient light on alertness and task performance focused on the field of lighting,while relatively few studies on screen blue light were conducted,and factors such as screen brightness and task difficulty were not taken into account.Therefore,this paper will discuss this.This paper includes two studies.Study 1: the effect of different blue light levels on alertness.In order to explore the influence of different blue light levels on people’s alertness and task performance,a single-factor experimental design was adopted.The experimental task was a relatively simple button response task,in which the subjects were required to respond to two kinds of stimuli(rectangle and diamond)respectively.Since the task was simple and easy to learn,the practice effect could be effectively avoided.The independent variables were different blue light levels(0%,50%,100%).KSS subjective scale score,key response accuracy,reaction time and brainwave were selected as measurement indicators.The results were consistent among KSS subjective score,keystroke response time,and theta signals.Higher screen blue light levels were associated with lower subjective sleepiness,faster keystroke response,and lower theta waves.Study 2:the effects of different levels of blue light and task difficulty on working memory performance.In order to explore the effects of different blue light levels and task difficulty on individual alertness and task performance,3(screen blue light level: 0%,50%,100%)×2(task difficulty: 2-back,3-back)was used as an in-subject experiment design.Subjects had to perform 2-back and 3-back working memory tasks at different levels of blue light.KSS subjective scale score,response time and accuracy of working memory tasks,and EEG data(P300 mean amplitude)were selected as observational indicators.The results showed that the response time of 2-back task was affected by different levels of blue light.The higher the level of blue light was,the shorter the response time was.There was no significant effect on response to the 3-back task.In addition,the EEG data results showed no significant differences in the average P300 amplitude of the brain between different blue light levels and significant differences between tasks.The average amplitude of P300 was significantly higher in the memory task with low difficulty.Under the research conditions of this paper,the following conclusions can be obtained:1)In the scene with the same screen brightness,the higher the level of blue light,the higher the level of alert,and the better performance of sustained attention task;2)Different levels of blue light had a greater effect on tasks with lower working memory difficulty,showing greater alertness,but had little effect on difficult tasks.High levels of blue light made subjects perform better on tasks with less difficulty in working memory.