Biomedical Engineering Laboratory, Department of Electrical Engineering, and Advanced Mining Technology Center, Universidad de Chile, Casilla 412-3, Av. Tupper 2007, Santiago, Chile.
BMC Neurosci. 2010 Jun 18;11:76. doi: 10.1186/1471-2202-11-76.
The tactile sense is being used in a variety of applications involving tactile human-machine interfaces. In a significant number of publications the classical threshold concept plays a central role in modelling and explaining psychophysical experimental results such as in stochastic resonance (SR) phenomena. In SR, noise enhances detection of sub-threshold stimuli and the phenomenon is explained stating that the required amplitude to exceed the sensory threshold barrier can be reached by adding noise to a sub-threshold stimulus. We designed an experiment to test the validity of the classical vibrotactile threshold. Using a second choice experiment, we show that individuals can order sensorial events below the level known as the classical threshold. If the observer's sensorial system is not activated by stimuli below the threshold, then a second choice could not be above the chance level. Nevertheless, our experimental results are above that chance level contradicting the definition of the classical tactile threshold.
We performed a three alternative forced choice detection experiment on 6 subjects asking them first and second choices. In each trial, only one of the intervals contained a stimulus and the others contained only noise. According to the classical threshold assumptions, a correct second choice response corresponds to a guess attempt with a statistical frequency of 50%. Results show an average of 67.35% (STD = 1.41%) for the second choice response that is not explained by the classical threshold definition. Additionally, for low stimulus amplitudes, second choice correct detection is above chance level for any detectability level.
Using a second choice experiment, we show that individuals can order sensorial events below the level known as a classical threshold. If the observer's sensorial system is not activated by stimuli below the threshold, then a second choice could not be above the chance level. Nevertheless, our experimental results are above that chance level. Therefore, if detection exists below the classical threshold level, then the model to explain the SR phenomenon or any other tactile perception phenomena based on the psychophysical classical threshold is not valid. We conclude that a more suitable model of the tactile sensory system is needed.
触觉在涉及触觉人机界面的各种应用中得到了广泛应用。在大量出版物中，经典阈值概念在建模和解释心理物理实验结果（如随机共振 (SR) 现象）中起着核心作用。在 SR 中，噪声增强了亚阈值刺激的检测，并且通过向亚阈值刺激添加噪声，可以达到超过感觉阈值障碍所需的幅度来解释该现象。我们设计了一个实验来测试经典振动触觉阈值的有效性。使用二次选择实验，我们表明个体可以对低于经典阈值水平的感觉事件进行排序。如果观察者的感觉系统没有被低于阈值的刺激激活，那么二次选择就不能高于机会水平。然而，我们的实验结果高于该机会水平，与经典触觉阈值的定义相矛盾。
我们对 6 名受试者进行了三次选择强制选择检测实验，要求他们进行第一次和第二次选择。在每次试验中，只有一个间隔包含刺激，其他间隔只包含噪声。根据经典阈值假设，正确的第二次选择响应对应于具有 50%统计频率的猜测尝试。结果显示，第二次选择响应的平均正确率为 67.35%（标准差为 1.41%），这无法用经典阈值定义来解释。此外，对于低刺激幅度，第二次选择的正确检测在任何可检测水平上都高于机会水平。
使用二次选择实验，我们表明个体可以对低于经典阈值水平的感觉事件进行排序。如果观察者的感觉系统没有被低于阈值的刺激激活，那么二次选择就不能高于机会水平。然而，我们的实验结果高于该机会水平。因此，如果在经典阈值水平以下存在检测，则基于心理物理经典阈值的 SR 现象或任何其他触觉感知现象的解释模型是无效的。我们得出结论，需要一种更适合触觉感觉系统的模型。
