Minimum change method to measure color brightness difference discrimination threshold experiment report

1 Introduction The method of minimal change is one of three methods proposed by GTFechner (1860) for measuring sensory thresholds. The difference threshold is the value of the smallest difference between two stimuli (the same physical quantity) that we can just sense. It is generally expressed in DL. When the sensory threshold is measured by the minimum change method, the stimulus is usually arranged in series according to physical strength, and the intensity difference between adjacent stimuli is small, and the change in stimuli intensity should be kept equal. When using the minimum variation method to determine the threshold, it is possible that the habitual error and the expected error occur. In order to eliminate these two errors, when ↓ and ↑ are used twice each, the stimuli are presented in the order of ↓↑↑↓ or ,. When ↓ and ↑ are used four times each, press ↓↑↑↓↑↓↓. The order of moles presents a stimulus.
This experiment uses the minimum change method to determine the color brightness difference threshold. Usually when an individual perceives changes in the brightness of visual stimuli, there is a limit to the perception of changes in the brightness of stimuli. When the magnitude of lightness changes is small, we are usually unaware of it, and when the brightness changes to a certain extent At that time, we can feel the existence of the difference in brightness of the two stimuli before and after. Then, the smallest change in brightness perceived by the individual is the difference in brightness. When the color of the stimulus changes, the difference threshold of the individual's brightness changes will also change accordingly. In this experiment, the difference in the brightness difference between the different colors is determined, and the influence of the color on the discrimination threshold of the brightness difference is discussed.
2 experiments
2.1 The purpose of the experiment
2.1.1 Discern the difference thresholds by measuring the chromaticity of different colors, and learn to measure the difference threshold using the traditional psychophysical-minimum variation method.
2.1.2 Grasp the various factors that brightness measurement should control
2.1.3 Check whether there are significant differences in the brightness thresholds of different colors
2.2 Experimental Methods
2.2.1 One of the Grade 04 classmates of the Department of Psychology of the Institute of Assemblies, male, 21 years old, with correct vision correction and no color perception disorder.
2.2.2 Experimental apparatus and experimental materials The experimental procedure of “Measurement of difference in color brightness difference by mean difference method” of Beijing Normal University was used. There are 2 colors in the different colored cubes presented by the computer: red and blue, and the RGB() function value for each color standard stimulus and comparison stimulus is as follows:
The parameter values ​​of the RGB() function for each color standard stimulus
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Color RGB() function value Red RGB(120,0,0)
Blue RGB(0,0,120)
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2.2.3 Experiment Procedure First double-click the experimental program icon to enter the experiment state. There are four kinds of colors (red/green/yellow/blue) in the color main menu. Click the corresponding color options to experiment. . In this experiment, the minimum difference between the stimulus and standard stimulus brightness changes has been determined, so the preliminary experiment is omitted. The experimental materials are red, yellow, green and blue. In the "experimental material", the experiment color was selected and the guideline appeared on the screen. The subjects carefully read the instruction. The experiment presents two colors of stimuli. One is a standard stimulus, one is a comparative stimulus, the standard stimulus is sometimes on the left, and sometimes on the right. It is required to compare the presented comparative stimulus with the standard stimulus, and then determine whether the comparative stimulus is darker or lighter than the standard stimulus and determine whether it is ` Depth, shallow or equal. If the report is 'deep', press the up arrow; if the report is 'equal', press the space bar; if the report is 'light', press the arrow. Whenever the response of the subject had a turning point, the next measurement was started. The stimuli for each color appear as follows (in red, for example), for a total of 16 times. The blue experiment is the same as above.
Rendering series of red stimuli and standard/comparatively stimulating positions
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Standard (S)/Comparison (C)
Motivation location SC CS CS SC
Stimulus series ↑↓↓↑ ↓↑↑↓ ↑↓↓↑ ↓↑↑↓
Remarks Each value of the stimulating RGB() function is randomly presented within a certain range above and below the standard stimulus.
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Note: S is the standard stimulus C is more stimulating
2.3 Experimental results Record of the results of differential threshold of red stimulus Standard stimulus(S)/Comparative stimulus(C)
Motivation location SC CS CS SC
Stimulus series ↓ ↑ ↑ ↓ ↑ ↓ ↓ ↑ ↑ ↓ ↓ ↓ ↑ ↑ ↑ ↓
On the DL 106 98 98 105 96 105 99 98 109 103 102 89 113 98 101 101
DL 102 94 94 99 92 103 97 96 107 101 100 87 111 94 95 99
Record of results of differential thresholds for blue stimuli Standard Stimulus (S)/Comparative Stimulus (C)
Motivation location SC CS CS SC
Stimulus series ↓ ↑ ↑ ↓ ↑ ↓ ↓ ↑ ↑ ↓ ↓ ↓ ↑ ↑ ↑ ↓
On the DL 100 94 106 101 86 101 99 98 97 105 98 95 103 100 105 113
Under the DL 94 92 96 95 84 97 93 94 93 101 94 91 99 96 101 109

Red Blue Average Upper Limit 101.3125 100.0625
The average lower limit of 98.1875 95.5625
Not sure about the pitch 3.125 4.5
Differential threshold 1.5625 2.25

Two groups of experimental data were used to test the significance of the mean difference between the independent small samples, t = 2.327, 0.01 <P <0.05, so the subjects had significant differences in the brightness difference threshold between red and blue.
3 Discussion
3.1 In the implementation process of the experiment, because the participants finished the two colors together, there was little fatigue; the experiment effect was produced later in the experiment. In terms of error control, in order to avoid spatial errors, the number of times the standard stimulus is on the left and on the right is half; in order to avoid the sequence error, the stimulus is presented with the series of ↓↑↑↓ and ↑↓↓↑ stimulation, and the whole experiment process uses multiple ABBA methods. . But at the same time also found some interference factors, the subjects were psychological students, have a certain understanding of the principles and methods of the experiment, so produce the expected error.
3.2 Since we have different visual sensitivities to different wavelengths or colors of stimuli, the susceptibility to changes in lightness will be affected to some extent, and there will be some differences in the lightness threshold.
3.3 If the difference in the intensity of adjacent stimuli is too small in the experiment, there will be no benefit to increase the number of times the stimuli are presented. If the difference in stimuli intensity is too large, the error of the results will increase. This experiment was conducted through pre-experimental measurements. More reliable.
4 Conclusion
4.1 There were significant differences in the threshold of brightness difference between the two colors of red and blue.
4.2 It is more accurate to use the minimum change method to measure the difference in brightness of different colors.