Iwaniuk Andrew N, Dean Karen M, Nelson John E
School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
Brain Behav Evol. 2005;65(1):40-59. doi: 10.1159/000081110. Epub 2004 Sep 30.
Despite significant progress in understanding the evolution of the mammalian brain, relatively little is known of the patterns of evolutionary change in the avian brain. In particular, statements regarding which avian taxa have relatively larger brains and brain regions are based on small sample sizes and statistical analyses are generally lacking. We tested whether psittaciforms (parrots, cockatoos and lorikeets) have larger brains and forebrains than other birds using both conventional and phylogenetically based methods. In addition, we compared the psittaciforms to primates to determine if cognitive similarities between the two groups were reflected by similarities in brain and telencephalic volumes. Overall, psittaciforms have relatively larger brains and telencephala than most other non-passerine orders. No significant difference in relative brain or telencephalic volume was detected between psittaciforms and passerines. Comparisons of other brain region sizes between psittaciforms and other birds, however, exhibited conflicting results depending upon whether body mass or a brain volume remainder (total brain volume - brain region volume) was used as a scaling variable. When compared to primates, psittaciforms possessed similar relative brain and telencephalic volumes. The only exception to this was that in some analyses psittaciforms had significantly larger telencephala than primates of similar brain volume. The results therefore provide empirical evidence for previous claims that psittaciforms possess relatively large brains and telencephala. Despite the variability in the results, it is clear that psittaciforms tend to possess large brains and telencephala relative to non-passerines and are similar to primates in this regard. Although it could be suggested that this reflects the advanced cognitive abilities of psittaciforms, similar studies performed in corvids and other avian taxa will be required before this claim can be made with any certainty.
尽管在理解哺乳动物大脑进化方面取得了重大进展，但对于鸟类大脑进化变化的模式却知之甚少。特别是，关于哪些鸟类分类群具有相对较大的大脑和脑区的说法，是基于小样本量，并且普遍缺乏统计分析。我们使用传统方法和基于系统发育的方法，测试了鹦鹉形目（鹦鹉、凤头鹦鹉和吸蜜鹦鹉）的大脑和前脑是否比其他鸟类更大。此外，我们将鹦鹉形目与灵长类动物进行比较，以确定两组之间的认知相似性是否通过大脑和端脑体积的相似性来体现。总体而言，鹦鹉形目的大脑和端脑相对比大多数其他非雀形目鸟类更大。在鹦鹉形目和雀形目之间，未检测到相对脑体积或端脑体积的显著差异。然而，根据是将体重还是脑体积余数（总脑体积 - 脑区体积）用作缩放变量，鹦鹉形目与其他鸟类之间其他脑区大小的比较呈现出相互矛盾的结果。与灵长类动物相比，鹦鹉形目具有相似的相对脑体积和端脑体积。唯一的例外是，在一些分析中，鹦鹉形目的端脑比脑体积相似的灵长类动物明显更大。因此，这些结果为之前关于鹦鹉形目具有相对较大的大脑和端脑的说法提供了实证依据。尽管结果存在差异，但很明显，相对于非雀形目鸟类，鹦鹉形目往往具有较大的大脑和端脑，在这方面与灵长类动物相似。虽然可以认为这反映了鹦鹉形目的高级认知能力，但在能够确定地做出这一断言之前，还需要对鸦科和其他鸟类分类群进行类似的研究。
