Eleven-month-old infants infer differences in the hardness of object surfaces from observation of penetration events.

Examples of stimuli used in Experiments 1 and 2. In Experiment 1, we manipulated three velocity changes (deceleration, constant velocity, and acceleration) involving the stick’s velocity during the “before penetration” and “penetration” phases, creating two different types of stimuli in which the surfaces of the hemispheric objects were perceived by adult observers as relatively “soft” or “crusty” (Masuda et al., 2011). Two of the three velocity changes were combined. For one of the “soft” videos, the stick accelerated before penetration and then moved at a constant speed during penetration (Soft 1). The other “soft” video involved constant velocity of the stick before penetration and deceleration during penetration (Soft 2). In contrast, for one of the “crusty” stimuli, the stick approached at constant speed and then accelerated during penetration (Crusty 1). The other “crusty” video involved deceleration of the stick before penetration followed by constant velocity during penetration (Crusty 2). In Experiment 2, the stimulus videos were identical to those used in Experiment 1, except that the gray hemisphere was deleted from the videos in the current experiment.

实验1与实验2所使用的刺激材料示例如下。在实验1中，我们通过操控“穿透前（before penetration）”与“穿透（penetration）”阶段中棒状物的三种速度变化（减速（deceleration）、匀速（constant velocity）与加速（acceleration）），将其中两种速度变化进行组合，生成了两类不同的刺激材料——成年观察者会将此类半球形物体的表面感知为相对“柔软”或“硬脆”（Masuda等人，2011）。其中一段“柔软”类视频的棒状物在穿透前加速，穿透阶段保持匀速（柔软1）；另一段“柔软”类视频的棒状物在穿透前保持匀速，穿透阶段减速（柔软2）。与之相对，一段“硬脆”类刺激的棒状物以匀速接近，穿透阶段加速（硬脆1）；另一段“硬脆”类视频的棒状物在穿透前减速，穿透阶段保持匀速（硬脆2）。实验2中的刺激视频与实验1所用材料完全一致，仅在本实验的视频中移除了灰色半球形物体。