Quick responses to fast changes in the environment are crucial in animal behaviour and survival, for example to seize prey, escape predators, or negotiate obstacles. Here, we study the ‘simple response time’ that is the time elapsed between receptor stimulation and motor activation as typically shown in escape responses, for mobile organisms of various taxa ranging from bacteria to large vertebrates. We show that 95% of these simple response times lie within one order of magnitude of the overall geometric mean of about 25ms, which is similar to that of a well-studied sensory time scale, the inverse of the critical flicker fusion frequency in vision, also lying within close bounds for all the organisms studied. We find that this time scale is a few times smaller than the minimum time to move by one body length, which is known to lie also within a relatively narrow range for all moving organisms. The remarkably small 10²-fold range of the simple response time among so disparate life forms varying over 10²⁰-fold in body mass suggests that it is determined by basic physicochemical constraints, independently on the structure and scale of the organism. We thus propose first-principle estimates of the simple response and sensory time scales in terms of physical constants and a few basic biological properties common to mobile organisms and constraining their responses.

对环境快速变化的快速反应对于动物行为和生存至关重要，例如捕捉猎物、逃避捕食者或克服障碍。在这里，我们研究了“简单反应时间”，即受体刺激和运动激活之间经过的时间，如逃逸反应中通常所示，对于从细菌到大型脊椎动物的各种分类群的移动生物。我们表明，这些简单响应时间的 95% 位于大约 25 毫秒的整体几何平均值的一个数量级内，这类似于经过充分研究的感官时间尺度，视觉中临界闪烁融合频率的倒数，也位于所有研究的生物体的密切范围内。我们发现这个时间尺度比移动一个身体长度的最小时间小几倍，众所周知，对于所有移动的生物，它也位于相对狭窄的范围内。非常小的10在如此不同的生命形式中，简单响应时间的²倍范围变化超过 10 ²⁰倍的体重表明它是由基本的物理化学约束决定的，与生物体的结构和规模无关。因此，我们根据物理常数和一些移动生物常见的基本生物学特性提出了简单反应和感官时间尺度的第一性原理估计，并限制了它们的反应。