Kanai Masaki, Matsui Hiroshi, Watanabe Shigeru, Izawa Ei-Ichi
Department of Psychology, Keio University, Tokyo, Japan.
Neuroreport. 2014 Sep 10;25(13):1064-8. doi: 10.1097/WNR.0000000000000229.
Birds are capable of dexterous sensory-motor activities such as tool use. Reaching is a crucial component of tool use and is a vision-guided behavior in primates, in which arm movement is monitored online in a stable visual frame. However, vision-guided reaching in primates is enabled by anatomical separation of the head and arm; neck reaching in birds accompanies head movement, which produces unstable vision because the eye necessarily moves with the bill. This anatomical difference raises the question whether tool use in birds involves visuomotor mechanisms that are distinct from those in primates. As the role of vision in avian tool use has been poorly understood, we investigated the role of vision in tool use in the large-billed crow (Corvus macrorhynchos), a nontool user in the wild. Crows were trained to manipulate an L-shaped hook to retrieve food that was otherwise out of reach. After training, an opaque panel was placed on the front window of the platform to block their vision, and the effects on tool use were tested with respect to performance and movement trajectory. Vision blocking caused similar deviation of tool movement trajectories for both near and far targets, as well as far target-specific deviation. This suggests the involvement of vision in tool use by crows, specifically in the premanipulation process for conversion of vision-body coordinates for motor planning and in the process of tool manipulation. This is the first behavioral evidence for the involvement of vision in avian tool use.
鸟类能够进行灵巧的感觉运动活动，比如使用工具。伸手够物是使用工具的关键组成部分，在灵长类动物中是一种视觉引导行为，其中手臂运动在稳定的视觉框架内进行在线监测。然而，灵长类动物的视觉引导伸手够物是通过头部和手臂的解剖分离实现的；鸟类的颈部够物伴随着头部运动，这会产生不稳定的视觉，因为眼睛必然会随着喙一起移动。这种解剖学差异引发了一个问题，即鸟类使用工具是否涉及与灵长类动物不同的视觉运动机制。由于视觉在鸟类使用工具中的作用一直未得到充分理解，我们研究了视觉在大嘴乌鸦（Corvus macrorhynchos）使用工具中的作用，这种乌鸦在野外不使用工具。训练乌鸦操纵一个L形钩子来获取原本够不到的食物。训练后，在平台的前窗放置一块不透明的面板以阻挡它们的视线，并测试对工具使用在性能和运动轨迹方面的影响。遮挡视线会导致远近目标的工具运动轨迹出现类似偏差，以及远距离目标特有的偏差。这表明视觉参与了乌鸦使用工具的过程，特别是在将视觉 - 身体坐标转换用于运动规划的预操作过程以及工具操作过程中。这是视觉参与鸟类使用工具的首个行为证据。
