# A New Framework of Human Interaction Recognition Based on Multiple Stage Probability Fusion
## 5 Algorithm Verification and Results Analysis
### Algorithm Tested in UT-Interaction Dataset
#### 5.1.2 Weighted Fusion Test  
(1) **At the start stage of the interaction,** the regions of the left and right sides of the moving target are extracted respectively, and the regions of interest are described by using HOG descriptors. The probability similarity of them are obtained by using a HMM which contain five hidden nodes. The final recognition results are obtained by weighted fusion of their probabilities similarity. The optimal weights are obtained by a large number of experiments, as shown in Figure 11a. The optimal weights of weighted fusion are 18% and 82% respectively. The final confusion matrix of recognition results in the start stage is as shown in Figure 11b. At the start stage of interactive behavior, the characteristics of the action are often not obvious, and some actions at the start stage are very similar, so the recognition result of the single atom action at the start stage is not good. However, the performance of recognition has been greatly improved by weighted fusing. Experimental results are shown in Table 1.  
Figure 11: (**a**) Weighted fusion optimal parameters test, (**b**) confusion matrix of recognition results after the weighted fusion of the start stage (Average recognition rate: 78%). Figure 10: The relationship between the average recognition rate and the number of the HMM’s hidden nodes in the end stage of the interaction behavior, (**a**) the left side, (**b**) the right. (2) **At the end stage of the interaction,** the regions of the left and right sides of the moving target are extracted respectively, and the regions of interest are described by using HOG descriptors. The probability similarity of them are obtained by using a HMM which contains two hidden nodes. The final recognition results are obtained by weighted fusion of their similar probabilities. As was the case with the start stage, the recognition results of the single atom behavior are not good, but after the weighted fusion, the performance of recognition has been greatly improved. Experimental results are shown in Table 2.  
The optimal weights are obtained by a large number of experiments, as shown in Figure 12a, the optimal weights of weighted fusion are 17% and 83% respectively. The final confusion matrix of the recognition results after the weighted fusion of the start stage is shown in Figure 12b. (3) **Weighted fusion of similar probabilities of the three stages. ** According to the weighted fusion process of the start stage and the end stage, it can be found that the average recognition rate is related to the optimal weights in the weighted fusion of the different stages of the interaction behavior. In the process of weighted fusion, the weights are set according to the recognition results of the different stages in this paper. The weight of the similar probability at the start stage is 20% (the average recognition rate of this stage is 78%). The weight of the similar probability of the middle stage is 48% (the average recognition rate of this stage is 92%). The weight of the similar probability of the middle stage is 32% (the average recognition rate of this stage is 80%). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Action Type** & **Hand Shake** & **Hug** & **Kick** & **Punch** & **Push** & **Avr\%** \\ \hline Left & 80 & 40 & 50 & 50 & 50 & 54 \\ Right & 90 & 90 & 60 & 60 & 70 & 74 \\ Final & 90 & 90 & 70 & 70 & 70 & 78 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Recognition results of single atom behavior and weighted fusion recognition results of start stage. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Action Type** & **Hand Shake** & **Hug** & **Kick** & **Punch** & **Push** & **Avr\%** \\ \hline Left & 100 & 80 & 40 & 50 & 70 & 68 \\ Right & 70 & 70 & 90 & 50 & 80 & 72 \\ Final & 90 & 70 & 90 & 70 & 80 & 80 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Recognition results of single atom behavior and weighted fusion recognition results of end stage.