Wolfson Centre for Cognitive Neuroscience, School of Psychology, Bangor University Bangor, UK ; Behavioural Brain Science Centre, School of Psychology, University of Birmingham Birmingham, UK.
Wolfson Centre for Cognitive Neuroscience, School of Psychology, Bangor University Bangor, UK.
Front Psychol. 2014 Feb 14;5:109. doi: 10.3389/fpsyg.2014.00109. eCollection 2014.
When we hold an object while looking at it, estimates from visual and haptic cues to size are combined in a statistically optimal fashion, whereby the "weight" given to each signal reflects their relative reliabilities. This allows object properties to be estimated more precisely than would otherwise be possible. Tools such as pliers and tongs systematically perturb the mapping between object size and the hand opening. This could complicate visual-haptic integration because it may alter the reliability of the haptic signal, thereby disrupting the determination of appropriate signal weights. To investigate this we first measured the reliability of haptic size estimates made with virtual pliers-like tools (created using a stereoscopic display and force-feedback robots) with different "gains" between hand opening and object size. Haptic reliability in tool use was straightforwardly determined by a combination of sensitivity to changes in hand opening and the effects of tool geometry. The precise pattern of sensitivity to hand opening, which violated Weber's law, meant that haptic reliability changed with tool gain. We then examined whether the visuo-motor system accounts for these reliability changes. We measured the weight given to visual and haptic stimuli when both were available, again with different tool gains, by measuring the perceived size of stimuli in which visual and haptic sizes were varied independently. The weight given to each sensory cue changed with tool gain in a manner that closely resembled the predictions of optimal sensory integration. The results are consistent with the idea that different tool geometries are modeled by the brain, allowing it to calculate not only the distal properties of objects felt with tools, but also the certainty with which those properties are known. These findings highlight the flexibility of human sensory integration and tool-use, and potentially provide an approach for optimizing the design of visual-haptic devices.
当我们在观察物体时拿着它，视觉和触觉线索对大小的估计会以统计上最优的方式结合在一起，从而赋予每个信号的“权重”反映了它们的相对可靠性。这使得物体的属性可以被更精确地估计，而不是仅凭单一感觉。钳子和镊子等工具系统地改变了物体大小与手张开之间的映射关系。这可能会使视觉-触觉整合变得复杂，因为它可能会改变触觉信号的可靠性，从而破坏适当信号权重的确定。为了研究这一点，我们首先使用具有不同“增益”（通过立体显示器和力反馈机器人创建）的类似钳子的虚拟工具来测量触觉大小估计的可靠性。工具使用中的触觉可靠性可以通过对手张开变化的敏感性和工具几何形状的影响的简单组合来确定。对手张开的敏感性的精确模式违反了韦伯定律，这意味着触觉可靠性随工具增益而变化。然后，我们检查了视动系统是否会考虑到这些可靠性变化。我们通过测量视觉和触觉刺激的权重来测量这些变化，再次使用不同的工具增益，方法是测量视觉和触觉尺寸独立变化时刺激的感知大小。每个感觉线索的权重随工具增益而变化，这种变化方式与最佳感觉整合的预测非常相似。这些结果与大脑对不同工具几何形状进行建模的想法一致，这使得它不仅可以计算用工具感觉到的物体的远端属性，还可以计算这些属性的确定性。这些发现突出了人类感觉整合和工具使用的灵活性，并为优化视觉-触觉设备的设计提供了一种方法。
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