Schmidt Filipp, Fleming Roland W, Valsecchi Matteo
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J Vis. 2020 Jun 3;20(6):2. doi: 10.1167/jov.20.6.2.
Object shape is an important cue to material identity and for the estimation of material properties. Shape features can affect material perception at different levels: at a microscale (surface roughness), mesoscale (textures and local object shape), or megascale (global object shape) level. Examples for local shape features include ripples in drapery, clots in viscous liquids, or spiraling creases in twisted objects. Here, we set out to test the role of such shape features on judgments of material properties softness and weight. For this, we created a large number of novel stimuli with varying surface shape features. We show that those features have distinct effects on softness and weight ratings depending on their type, as well as amplitude and frequency, for example, increasing numbers and pointedness of spikes makes objects appear harder and heavier. By also asking participants to name familiar objects, materials, and transformations they associate with our stimuli, we can show that softness and weight judgments do not merely follow from semantic associations between particular stimuli and real-world object shapes. Rather, softness and weight are estimated from surface shape, presumably based on learned heuristics about the relationship between a particular expression of surface features and material properties. In line with this, we show that correlations between perceived softness or weight and surface curvature vary depending on the type of surface feature. We conclude that local shape features have to be considered when testing the effects of shape on the perception of material properties such as softness and weight.
物体形状是识别材料特性以及估计材料属性的重要线索。形状特征可在不同层面影响材料感知：微观层面（表面粗糙度）、中观层面（纹理和局部物体形状）或宏观层面（整体物体形状）。局部形状特征的例子包括布料上的褶皱、粘性液体中的凝块或扭曲物体上的螺旋形折痕。在此，我们着手测试此类形状特征在材料属性柔软度和重量判断中的作用。为此，我们创建了大量具有不同表面形状特征的新颖刺激物。我们发现，这些特征根据其类型以及幅度和频率，对柔软度和重量评级有不同影响，例如，尖刺数量增加和尖锐程度提高会使物体显得更硬更重。通过让参与者说出与我们的刺激物相关联的熟悉物体、材料和转变，我们可以表明，柔软度和重量判断并非仅仅源于特定刺激物与现实世界物体形状之间的语义关联。相反，柔软度和重量是根据表面形状估计出来的，大概是基于对表面特征的特定表现与材料属性之间关系的习得启发式方法。与此相符的是，我们表明，感知到的柔软度或重量与表面曲率之间的相关性因表面特征类型而异。我们得出结论，在测试形状对诸如柔软度和重量等材料属性感知的影响时，必须考虑局部形状特征。
