# Quantitative Classification Model of Composite Product Image Based on Event-Related Potential
## 3 Analysis of Experimental Data
### ERP Experimental Data Analysis
#### 3.2.5 Target Phase N400  
For the N400 component, the average amplitude of the ERP in the 250-400 ms period during the start phase was selected for RMANOVA, and the distribution positions of the brain electrodes (Hortal electrodes (AF3 and AF4), top electrodes (FC1 and FC2) and occipital electrodes (O1 and O2)) were taken as the intergroup variables; three groups of image word pairs (\"classical-modern\", \"tough-round\" and \"speed-steady\"); and three types of semantic matchings (image consistent, image neutral and image inconsistent)  
Figure 10: P300 component waveform of three pairs of image words at electrode POZ. Green dashed rectangles mark the 200–300-ms time window.  
were used as the within-group variables. The results showed that image word pairs, semantic matching and distribution of electrodes in brain regions all had some effect on the average amplitude of the N400 components. Image word pairs had a main effect, F (1.757, 33.374) = 5.986, \(p\) = 0.008; semantic matching had a significant main effect, F (1.954, 31.123) = 8.626, \(p\) = 0.001. There was a significant main effect on the location of electrodes in the brain region, F (5, 15) = 14.717, \(p\) < 0.001. There was a significant interaction between image word pairs and semantic matching, F (3.039, 57.750) = 4.757, \(p\) = 0.005. There was an interactive effect between the location of the electrodes in the brain area and semantic matching, F (10, 10) = 3.924, \(p\) = 0.021.  
The paired t-test of the electrode distribution in the brain region shows that electrode FC2 has a higher N400 amplitude than other electrodes, and the difference was very significant, as shown Figure 11. Therefore, electrode FC2 was selected as the target electrode for the N400 components in the initial phase of the research.  
For each group of image-word pairs in the FC2 electrode, the stimulus materials with different levels of degrees of semantic matching induced N400 components with different amplitudes, with the image-neutral induced N400 amplitude being the highest, followed by the image-inconsistent and the image-consistent induced N400 amplitude being the lowest. Based on the paired t-test of three image-word pairs with different degrees of semantic matching, it can be seen that the amplitude of the N400 waveform was slightly different among the three groups of image-word pairs. For the word pair \"classical-modern\", the N400 amplitude of image neutral was the largest, and the N400 amplitude of image consistent was the smallest. There was a significant difference between image consistent and image neutral, t = 3.921, \(p\) = 0.001. There was a significant difference between image consistent and image inconsistent, t = 2.692, \(p\) = 0.014. There was a significant difference between image neutral and image inconsistent, t = -3.383, \(p\) = 0.003. For the \"tough-round\" word pair, the N400 amplitude of image neutral was the largest, and the N400 amplitude of image consistent was the smallest. The difference between image consistent and image  
Figure 11: N400 component waveforms of three pairs of image words at electrode FC2. Green dashed rectangles mark the 250–400-ms time window.  
neutral was significant, t = 3.335, \(p\) = 0.004. The difference between image consistent and image inconsistent was significant, t = 2.579, \(p\) = 0.019. The difference between image neutral and image inconsistent was significant, t = \(-\)2.741, \(p\) = 0.013. For the word pair of \"speed-stable\", the difference between image neutral and image inconsistent was not significant, the N400 amplitude of image neutral was the lowest, the difference between image consistent and image inconsistent was significant, t = 2.192, \(p\) = 0.043, and the difference between image neutral and image consistent was significant, t = 2.336, \(p\) = 0.035.