Hypothesis 3: Intraspecific growth patterns with age predictable by overall brain size, or growth reflecting important internal events.
Hypothesis 3: Growth patterns with age predictable by overall brain size, or growth reflecting important internal events.
Still, Dr. Castellanos, now at New York University's Child Study Center, said the difference in overall brain size was "not huge".
Deaner, R. O., Isler, K., Burkart, J. & van Schaik, C. Overall brain size, and not encephalization quotient, best predicts cognitive ability across non-human primates.
The findings, first published in the Proceedings of the National Academy of Sciences USA, are the first evidence that the capacity for learning in birds is closely related to brain structure, as opposed to overall brain size.
Species differences in overall brain size are strongly associated with brain allometry; relative sizes of visual processing tissues increase at faster rates than antennal processing tissues.
And brain imaging is notoriously noisy: not only does overall brain size vary from person to person, for instance, but so do the sizes of specialized brain regions like the hippocampus, which is critical for memory formation.
But they agreed on two findings: one gene that correlated strongly with overall brain size, and another that correlated with the rate at which the hippocampus atrophies, or shrinks, with age.
