Larger brain regions may have evolved to improve the way animals perceive the world, increasing both the amount of information they can process and the accuracy of that processing, according to new research from the University of Bath’s Department of Psychology.
Reports that large brains are unnecessary or merely evolutionary accidents have grown more common. This new study argues the opposite: expansion of specific brain areas—most notably regions involved in vision—plays an essential role in the evolution of perception. Rather than overall brain size alone, the authors emphasise the functional importance of increases in the volume of specialised cortical areas.
The researchers analysed data across a range of primate species, including humans, apes, and monkeys, and found a consistent relationship between the size of the visual cortex and measurable improvements in visual processing. Species with a relatively larger visual cortex tended to show greater visual resolution and lower susceptibility to common visual illusions. In short, larger cortical visual areas were associated with more precise and reliable perception.
Dr Alexandra de Sousa, the study’s first author and an expert in brain evolution, summarised the findings: “Primates with a larger visual cortex demonstrate better visual resolution and reduced illusion strength. Essentially, the larger that specific brain area is, the stronger the visual processing capabilities appear to be.”
De Sousa and colleagues note that increases in brain region volume tend to reflect both a greater number of neurons and a higher likelihood of connections among those neurons. Those extra neurons and connections support more complex neural computations, which enable finer discrimination of visual details and improved robustness against misleading visual cues. In practice, that translates into better visual acuity and a reduced tendency to misperceive patterns or shapes.
Co-author Dr Michael Proulx, Senior Lecturer (Associate Professor) in Psychology, emphasised the study’s integrative approach: “This paper brings together microanatomy, macroanatomy and behaviour. By linking measures of visual performance with volumetric brain data and neuron counts, we provide a framework that connects brain structure to function across species.”
The research combined neuroanatomical volume measurements from de Sousa’s work with behavioural studies of visual acuity and illusion susceptibility compiled by Proulx. This comparative approach enabled the team to test whether anatomical expansion in a sensory area corresponds to predictable changes in perception. Their results indicate that volumetric increases in specialised areas are not neutral byproducts of evolution but likely reflect adaptive changes that enhance sensory performance.
The authors highlight several testable implications and directions for future research. The theoretical framework they present can be extended by collecting behavioural data from a broader set of species, by expanding comparative neuroanatomical datasets, and by examining other sensory systems and multisensory integration. They also suggest that, with sufficient fossil and anatomical evidence, it may become possible to infer aspects of perceptual ability in extinct species by estimating the relative sizes of relevant brain structures.
The paper, “What can volumes reveal about human brain evolution? A framework for bridging behavioral, histometric and volumetric perspectives,” is published in Frontiers in Neuroanatomy. The study presents a rigorous framework for interpreting volumetric brain data in functional and behavioural terms, particularly in relation to visual processing and perceptual accuracy.
Contact: Andy Dunne – University of Bath
Source: University of Bath press release
Image Source: The image is credited to FastePhoto and is listed as public domain
Original Research: Abstract for “What can volumes reveal about human brain evolution? A framework for bridging behavioral, histometric, and volumetric perspectives” by Alexandra A. de Sousa and Michael J. Proulx in Frontiers in Neuroanatomy. Published online June 25, 2014. doi:10.3389/fnana.2014.00051