The first is simply size. Flight imposes strict weight limits, so birds pack enormous numbers of very small neurons into very small brains. Their axons, the long cable-like fibers that transmit electrical and chemical signals between cells, are shorter.<\/p>\n
\u201cLong lines take time. Short lines speed everything up,\u201d Nieder said.<\/p>\n
The second factor is temperature. Humans\u2019 body temperature is about 36.6\u00b0 Celsius, while birds go up to 41, or even 42\u00b0. This higher body temperature speeds up all chemical processes in birds\u2019 bodies.<\/p>\n
\u201cEvery ion channel would open and close faster. Every transmitter would move through the synaptic cleft faster,\u201d Nieder explained. \u201cEvolution really took their bodies to the limit. This is life in the fast lane, not only in the brain, but also respiration, the cardiovascular system\u2014everything is going toward the limit in birds.\u201d<\/p>\n
But calling crows (or birds in general) decision-making speed demons comes with a few caveats.<\/p>\n
Picking the smartest<\/p>\n
First, the study included only two birds, a rather small sample. \u201cOn the one hand, that\u2019s a valid constraint,\u201d Nieder said. \u201cOn the other hand, when you look at monkey studies, that\u2019s the standard number of animals that we have for these very complex types of studies, combining behavior and electrophysiology.\u201d<\/p>\n
Also, the decision-making time of 235 milliseconds in crows and above 400 milliseconds in primates is not an absolute limit. These times apply to the random dot-motion task, which inherently requires waiting to see which way things are drifting.<\/p>\n
Finally, it might be hard to learn whether the results extend beyond corvids or crows specifically. \u201cThe problem with many other birds is that they are not as smart as corvids and crows and you need a smart bird in order to train it to do exactly this task,\u201d Nieder said.<\/p>\n
So far, he admitted, we can\u2019t be sure whether excellent decision-making skills of crows in his lab are due to birds\u2019 brains being speedy in general or to crows simply being smarter than other avians. \u201cAmong birds, the corvids are renowned to be extremely intelligent, so maybe there\u2019s something special about them,\u201d Nieder said.<\/p>\n