Sept. 17th: Evolution of the primate brain and cognition

What is absolute brain size

The direct physical measurement of an animal's brain in mass or volume.

What is relative brain size

The size of an animal's brain compared to its overall body size.

What is cranial capacity

The volume of the interior of the skull used as an estimate of brain size.

What is allometry

The study of how one part of an organism grows in relation to the whole organism or another part.

What is the encephalization quotient (EQ)

A measure of how much brain size differs from the expected brain size for an animal's body size.

What does an EQ greater than 1 mean

The animal has a larger brain than expected for its body size.

What does an EQ less than 1 mean

The animal has a smaller brain than expected for its body size.

Why does absolute brain size not automatically indicate intelligence

Brain size must be considered relative to body size

What is the relationship between brain size and body size in mammals

Brain size increases at a slower rate than body size.

What do departures from expected allometric growth suggest

They provide strong evidence that a trait is under selection.

Why are primates notable for EQ

Primates have the largest EQs and the greatest increase in EQ among mammals over time.

What are the three major regions of the vertebrate brain

Hindbrain, midbrain, forebrain

What is the primary function of the hindbrain

Basic life support and movement coordination.

What structures are included in the hindbrain

Medulla, pons, crerebellum

What does the midbrain primarily control

Orienting, attention, and movement

What is the forebrain

The region containing the olfactory bulbs, cerebral hemisphere, and internal structures such as the thalamus, basal ganglia, and hypothamus

What is the cerebral neocortex

The thin outer layer of neural tissue covering the cerebral hemispheres that supports complex cognition.

What functions does the neocortex support

Sensory information, movement, learning, memory, decision making, and other complex behaviors

What are three major structural changes in primate brains

Reduced olfactory bulbs, cortical expansion and folding (more surface area), expansion of the prefrontal cortex, and “connectivity” greater integration across brain regions

What is the fourth major change in primate brains

Greater connectivity and integration across brain regions.

What is the function of the occipital lobe

Visual perception.

What is the function of the parietal lobe

Tactile perception

What is the function of the temporal lobe

Hearing

What is the function of the frontal lobe

Executive functions such as planning

How does the human prefrontal cortex compare with a cat's

The prefrontal cortex is about 30% of the human brain versus 3% in cats.

When did non-allometric prefrontal enlargement originate

Around 19–15 million years ago in great apes.

When did a more human-like wider frontal lobe organization appear in Homo

Around 1.7–1.5 million years ago.

Why are brains metabolically expensive

The brain is about 2% of body weight but requires about 20% of energy.

What is the adaptive benefit of larger brains

They can process and store more information.

What does mosaic brain evolution mean

Selection can expand or reorganize particular brain systems without changing every part equally.

What are the two major hypotheses for primate brain evolution

The ecological intelligence hypothesis and social intelligence hypothesis.

What is the ecological intelligence hypothesis

Physical environmental challenges such as finding and extracting food selected for larger brains and advanced cognition.

How might extractive foraging favor larger brains

It requires spatial information storage

Why might frugivores have larger relative brains than folivores

Fruit is more spatially and temporally variable

What is the social intelligence hypothesis

Large brains evolved partly in response to the challenges of living in large and complex social groups.

Why could larger social groups favor larger brains

Individuals must track more relationships

What social abilities may be supported by large brains

Kin recognition

What is one limitation of the social intelligence hypothesis

Social complexity is difficult to measure and some solitary species have large brains.

Are the ecological and social intelligence hypotheses mutually exclusive

No; multiple evolutionary pressures can contribute to brain evolution.

What is the expansive tissue hypothesis

Large brains became possible through higher-quality diets and changes in energy allocation.

What factors supported human brain expansion according to the expansive tissue hypothesis

Higher-quality diets

What is the cultural intelligence hypothesis

Social learning

What physical tasks are associated with cultural intelligence

Understanding space

What social tasks are associated with cultural intelligence

Social learning

What did comparisons of children and apes show about cognition

Children were similar in physical cognition but more sophisticated in social cognition.

What is the overall conclusion about human brain evolution

Multiple hypotheses can contribute; brain evolution involved size

Why is brain size alone insufficient for comparing intelligence

Comparisons must consider body size

How did vertebrate brains evolve according to the lecture

Existing brain structures were modified

What distinguishes primate brain evolution

Changes in the neocortex

Why is primate brain evolution not a single upward trend

Different lineages experienced different patterns of expansion

What factors may have selected for enhanced cognitive abilities

Ecological challenges