User:TheRealBenSherman/sandbox

EQ and intelligence in animals

Intelligence in animals is hard to establish, but the larger the brain is relative to the body, the more brain weight might be available for more complex cognitive tasks. The EQ formula, as opposed to the method of simply measuring raw brain weight or brain weight to body weight, makes for a ranking of animals that coincide better with observed complexity of behaviour. A primary reason for the use of EQ instead of a simple brain to body mass ratio is that smaller animals tend to have a higher proportional brain mass, but do not show the same indications of higher cognition as animals with a high EQ. (Claire) The driving theorization behind the development of EQ is that an animal of a certain size requires a minimum number of neurons for basic functioning- sometimes referred to as a grey floor. There is also a limit to how large an animal's brain can grow given its body size- due to limitations like gestation period, energetics, and the need to physically support the encephalized region throughout maturation. (Shultz & Dunbar 2010) When normalizing a standard brain size for a group of animals a, a slope can be determined to show what a species’ expected brain to body mass ratio would be (figure 2). Species with brain to body mass ratios below this standard are nearing the grey floor, and do not need extra grey matter. Species which fall above this standard have more grey matter than is necessary for basic functions. Presumably these extra neurons are used for higher cognitive processes. (Shultz & Dunbar) Mean EQ for mammals is around 1, with, cetaceans and primates above 1, and insectivores and herbivores below. Large mammals tend to have the highest EQ’s of all animals, while small mammals and avians have similar EQ’s (Figure 1). This reflects major trends. One is that brain matter is extremely costly in terms of energy needed to sustain it.[20] Animals with nutrient rich diets tend to have higher EQ’s, which is necessary for the energetically costly tissue of brain matter. Not only is it metabolically demanding to grow throughout embryonic and postnatal development, it is costly to maintain as well. Arguments have been made that some carnivores may have higher EQ’s due to their relatively enriched diets, as well as the cognitive capacity required for effectively hunting prey.21][22] One example of this is the brain size of a wolf; about 30% larger than a similarly sized domestic dog, potentially derivative of different needs in their respective ways of life.[23] It is worth noting, however, that of the animals demonstrating the highest EQ's (see associated table), many are primarily frugivores, including apes, macaques, and proboscideans. This dietary categorization is significant to inferring the pressures which drive higher EQ’s. Specifically, frugivores must utilize a complex, trichromatic, map of visual space to locate and pick ripe fruits, and are able to provide for the high energetic demands of increased brain mass. (DeCasien) Another factor previously thought to have great impact on brain size is sociality and flock size.[24] This was a long standing theory until the correlation between frugivory and EQ was shown to be more statistically significant. While no longer the predominant inference as to selection pressure for high EQ, the social brain hypothesis still has some support. For example,(DeCasien) dogs (a social species) have a higher EQ than cats (a mostly solitary species). Animals with very large flock size and/or complex social systems consistently score high EQ, with dolphinsand orcas having the highest EQ of all cetaceans,[4] and humans with their extremely large societies and complex social life topping the list by a good margin.[1]

Criticism:

Recent research indicates that whole brain size is a better measure of cognitive abilities than EQ for non-human primates at least.[35] The relationship between brain-to-body mass ratio and complexity is not alone in influencing intelligence. Other factors, such as the recent evolution of the cerebral cortex and different degrees of brain folding,[36] which increases the surface area (and volume) of the cortex, are positively correlated to intelligence in humans.[37] EQ has flaws to its design when considering individual data points rather than a species as a whole. It is inherently biased given that the cranial volume of an obese and underweight individual would be roughly similar, but their body masses would be drastically different. Another difference of this nature is a lack of accounting for sexual dimorphism. For example, the female human generally has smaller cranial volume than the male, however this does not mean that a female and male of the same body mass would have different cognitive abilities. Considering all of these flaws, EQ should be a metric for interspecies comparison only, not intraspecies. (Claire)