de Froment Adrian J, Rubenstein Daniel I, Levin Simon A
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America.
PLoS Comput Biol. 2014 Dec 18;10(12):e1003937. doi: 10.1371/journal.pcbi.1003937. eCollection 2014 Dec.
The standard view in biology is that all animals, from bumblebees to human beings, face a trade-off between speed and accuracy as they search for resources and mates, and attempt to avoid predators. For example, the more time a forager spends out of cover gathering information about potential food sources the more likely it is to make accurate decisions about which sources are most rewarding. However, when the cost of time spent out of cover rises (e.g. in the presence of a predator) the optimal strategy is for the forager to spend less time gathering information and to accept a corresponding decline in the accuracy of its decisions. We suggest that this familiar picture is missing a crucial dimension: the amount of effort an animal expends on gathering information in each unit of time. This is important because an animal that can respond to changing time costs by modulating its level of effort per-unit-time does not have to accept the same decrease in accuracy that an animal limited to a simple speed-accuracy trade-off must bear in the same situation. Instead, it can direct additional effort towards (i) reducing the frequency of perceptual errors in the samples it gathers or (ii) increasing the number of samples it gathers per-unit-time. Both of these have the effect of allowing it to gather more accurate information within a given period of time. We use a modified version of a canonical model of decision-making (the sequential probability ratio test) to show that this ability to substitute effort for time confers a fitness advantage in the face of changing time costs. We predict that the ability to modulate effort levels will therefore be widespread in nature, and we lay out testable predictions that could be used to detect adaptive modulation of effort levels in laboratory and field studies. Our understanding of decision-making in all species, including our own, will be improved by this more ecologically-complete picture of the three-way tradeoff between time, effort per-unit-time and accuracy.
生物学中的标准观点是，所有动物，从大黄蜂到人类，在寻找资源和配偶并试图躲避捕食者时，都面临速度与准确性之间的权衡。例如，觅食者在隐蔽处之外花费越多时间收集有关潜在食物来源的信息，就越有可能对哪些来源最有价值做出准确决策。然而，当在隐蔽处之外花费的时间成本增加时（例如在有捕食者的情况下），最优策略是觅食者减少收集信息的时间，并接受其决策准确性相应下降。我们认为，这幅常见的图景缺少一个关键维度：动物在每单位时间内用于收集信息的努力程度。这很重要，因为能够通过调节每单位时间的努力水平来应对不断变化的时间成本的动物，不必像在相同情况下仅限于简单速度 - 准确性权衡的动物那样接受相同程度的准确性下降。相反，它可以将额外的努力用于（i）减少其收集的样本中感知错误的频率，或者（ii）增加每单位时间收集的样本数量。这两者都能使它在给定时间段内收集到更准确的信息。我们使用决策制定的经典模型（序贯概率比检验）的一个修改版本来表明，这种用努力替代时间的能力在面对不断变化的时间成本时赋予了适应性优势。我们预测，调节努力水平的能力因此在自然界中会广泛存在，并且我们列出了可测试的预测，可用于在实验室和实地研究中检测努力水平的适应性调节。通过这种关于时间、每单位时间的努力和准确性之间三方权衡的更完整生态图景，我们对包括我们自己在内的所有物种决策制定的理解将会得到改善。
