Biomedical Engineering Department, Florida International University, Miami, FL, 33174, USA,
Ann Biomed Eng. 2014 Jan;42(1):162-76. doi: 10.1007/s10439-013-0880-9. Epub 2013 Aug 1.
The pupil diameter (PD), controlled by the autonomic nervous system, seems to provide a strong indication of affective arousal, as found by previous research, but it has not been investigated fully yet. In this study, new approaches based on monitoring and processing the PD signal for off-line and on-line "relaxation" vs. "stress" differentiation are proposed. For the off-line approach, wavelet denoising, Kalman filtering, data normalization, and feature extraction are sequentially utilized. For the on-line approach, a hard threshold, a moving average window and three stress detection steps are implemented. In order to use only the most reliable data, two types of data selection methods (paired t test based on galvanic skin response (GSR) data and subject self-evaluation) are applied, achieving average classification accuracies up to 86.43 and 87.20% for off-line and 72.30 and 73.55% for on-line algorithms, with each set of selected data, respectively. The GSR was also monitored and processed in our experiments for comparison purposes, with the highest classification rate achieved being only 63.57% (based on the off-line processing algorithm). The overall results show that the PD signal is more effective and robust for differentiating "relaxation" vs. "stress," in comparison with the traditionally used GSR signal.
瞳孔直径（PD）受自主神经系统控制，似乎能强烈反映情感唤醒，这在前人的研究中已得到证实，但尚未得到充分研究。在这项研究中，提出了基于监测和处理 PD 信号的离线和在线“放松”与“压力”区分的新方法。对于离线方法，依次使用小波去噪、卡尔曼滤波、数据归一化和特征提取。对于在线方法，实现了硬阈值、移动平均窗口和三个压力检测步骤。为了只使用最可靠的数据，应用了两种类型的数据选择方法（基于皮肤电反应（GSR）数据的配对 t 检验和受试者自我评估），离线算法的平均分类准确率最高可达 86.43%和 87.20%，在线算法的平均分类准确率最高可达 72.30%和 73.55%，分别对应于每一组选择的数据。在实验中还监测和处理了 GSR 以进行比较，离线处理算法的最高分类率仅为 63.57%。总体结果表明，与传统使用的 GSR 信号相比，PD 信号在区分“放松”与“压力”方面更有效、更稳健。
