# Quantitative Classification Model of Composite Product Image Based on Event-Related Potential
## 3 Analysis of Experimental Data
### ERP Experimental Data Analysis
#### 3.2.3 Startup Phase N400  
For the N400 component, the average amplitude of the ERP in the period of 350-500 ms during the start phase was selected for RMANOVA, and the distribution position of the brain electrodes (frontal electrodes (AF3, AF4, F7 and F8), occipital electrodes (O1 and O2)) were taken as intergroup variables, three groups of image words pairs (classical-modern, tough-round and speed-steady) and three types of semantic matching (image consistent, image neutral and image inconsistent) were used as variables within the group. The results showed that image word pairs, semantic matching and electrode distribution in brain regions all had some influence on the average amplitude of N400 components. Image words pairs had a main effect, F (1.757, 33.374) = 5.989, \(p\) = 0.005; semantic matching had a significant main effect, F (1.656, 31.464) =17.811, \(p\) < 0.001; and there was a significant main effect on the location of electrodes in the brain area, F (5, 15) = 31.513, \(p\) < 0.001. There was a significant interaction between image word pairs and semantic matching, F (7, 16) = 4.596, \(p\) = 0.001. There was an interaction effect between brain region distribution and semantic matching, F (10, 10) = 5.528, \(p\) = 0.006. The paired t-test of the brain region electrode distribution position showed that electrode F8 had a higher N400 amplitude than other electrodes, and the difference was significant, as shown in Figure 7. Therefore, electrode F8 was selected as the target electrode for the N400 component in the initial phase of the research.  
For each type of image word pair in the F8 electrode, stimulus materials with different degrees of semantic matching induced N400 components with different amplitudes. Among them, the N400 amplitude induced using an image neutral was the highest, followed by an inconsistent image, and the N400 amplitude induced using an image consistent was the lowest. Paired t-tests with different levels of semantic matching were performed based on three groups of image words. For the three types of image-word pairs, the N400 waveform showed a relatively consistent trend, i.e., N400 with the highest amplitude induced using image neutral, followed by image inconsistent and N400 with the lowest amplitude induced using image consistent. For the \"classical-modern\" word pair, the difference between image consistent and image neutral was significant, t = 5.06, \(p\) < 0.001, the difference  
Figure 6: P300 component waveform of three pairs of image words at electrode AF3. Green dashed rectangles the 300–400-ms time window.  
between image consistent and image inconsistent was significant, t = 4.904, \(p\) < 0.001, and the difference between image neutral and image inconsistent was significant, t = \(-\)3.139, \(p\) = 0.005. For the \"tough round\" word pair, the difference between image consistent and image neutral was significant, t = 6.283, \(p\) < 0.001, the difference between image consistent and image inconsistent was significant, t = 4.928, \(p\) = 0.000, and the difference between image neutral and image inconsistent was significant, t = \(-\)3.28, \(p\) = 0.005. For the word pair of \"speed-steady\", the difference between image consistent and image neutral was significant, t = 4.962, \(p\) < 0.001, the difference between image consistent and image inconsistent was significant, t = 3.395, \(p\) = 0.004, and the difference between image neutral and image inconsistent was significant, t = \(-\)4.575, \(p\) < 0.001.