KARL LASHLEY (1890 - 1958)

What is psychobiology?

The study of the biological basis of behavior, learning, and memory.

Who was Karl Lashley?

Psychobiologist who studied brain mechanisms of learning and memory.

Education?

PhD in genetics (Johns Hopkins) under H. S. Jennings.

Career highlights?

- Influenced by John Watson - Worked at Minnesota, Chicago, Harvard - Director of Yerkes Primate Lab

What is mass action?

Learning depends on the amount of cortex damaged, not specific location.

Key idea of mass action?

The brain works as an integrated whole.

What is equipotentiality?

Any part of a functional brain region can take over the function of the whole.

Key implication?

Brain function is distributed, not strictly localized.

What is the engram?

The physical trace of memory in the brain.

What was Lashley’s conclusion about the engram?

He could not locate a single memory center; memory is distributed.

What was his famous conclusion idea?

“We know what the memory trace is not.”

Lashley’s major impact?

Supported distributed brain function over strict localization.

What was Lashley’s core idea?

Memory is distributed across the brain, not stored in one location.

DONALD HEBB (1904 - 1985)

Who was Donald Hebb?

Canadian psychologist who explained learning through neural networks.

What is a cell assembly?

Group of neurons that become linked through repeated activation.

Why are cell assemblies important?

A thought = activation of a neural network. They are the neural basis of ideas—activating part of the network activates the whole pattern.

What are phase sequences?

Chains of cell assemblies that fire in sequence to produce thought.

Why do they matter?

They explain how thinking unfolds over time rather than happening in isolated moments.

What is Hebb’s rule?

Neurons that fire together wire together.

What does Hebb’s rule explain?

How learning and memory are formed through experience-driven brain changes.

What did Hebb find about environments?

Enriched environments improve learning, while deprived environments weaken cognitive development.

What did he conclude about development?

Early experience strongly shapes intelligence; adult brains are less plastic than developing ones.

What is Hebb’s legacy?

He laid the foundation for modern neuroscience, AI learning models, and connectionist theories.

ROGER SPERRY (1913 - 1994)

Who was Roger Sperry?

A neuropsychologist who studied split-brain patients and discovered hemispheric specialization.

What is the split-brain procedure?

Surgical severing of the corpus callosum (sometimes optic chiasm), disconnecting the hemispheres.

What happens after the procedure?

The two hemispheres operate independently, with limited communication.

What did Sperry show?

That the left and right hemispheres have specialized and independent functions.

What does the left hemisphere specialize in?

Language, logic, and analytical processing.

What does the right hemisphere specialize in?

Spatial processing, imagery, and holistic perception.

Why is split-brain surgery used?

To treat severe, intractable epilepsy.

What is the outcome for patients?

Most function normally in daily life despite hemispheric separation.

What was Sperry’s view of consciousness?

Consciousness arises from brain activity but also influences behaviour (interaction between mind and brain).

What is Sperry’s main contribution?

He proved hemispheric specialization and advanced understanding of how brain systems generate consciousness.

What is ethology?

The scientific study of animal behavior in natural environments, focusing on instinct and evolution.

KEY ETHOLOGISTS

Who was Karl von Frisch?

An ethologist who studied honeybee communication and discovered the waggle dance.

Who was Konrad Lorenz?

An ethologist who studied imprinting in birds and instinctive behavior.

Who was Niko Tinbergen?

An ethologist who studied animal behavior and developed the four questions of ethology.

What is the first feature of the ethological attitude?

Behavior should be studied in natural, meaningful contexts.

What is the second feature?

Observation and description should come before explanation.

What is the third feature?

Multiple species should be studied for comparison.

What is the fourth feature?

Closely related species should be compared to understand evolution of behavior.

What is the fifth feature?

Natural behavior is preferred over lab-based behavior.

What is sociobiology?

The study of how evolution and genetics shape social behavior.

What is biogrammar?

Innate biological tendencies that structure human social behavior.

Why is biogrammar important?

It explains why humans easily learn certain social patterns.

What is the leash principle?

Culture is constrained by biological limits needed for survival.

What is evolutionary psychology?

The study of the mind as a product of evolution solving ancestral survival problems.

What is the sociobiological fallacy?

The mistake of assuming all behavior exists only to maximize gene reproduction.

What is one criticism of evolutionary theory?

Not all traits are direct adaptations.

What is another criticism?

Some traits were adaptive in the past but not in modern environments.

What is exaptation?

A trait that evolved for one function but is used for another.

What is a spandrel?

A by-product of evolution that was not directly selected for.

What is a final criticism of sociobiology?

It can be overly deterministic if misapplied to human behavior.

Who were Keller and Marian Breland?

Behaviorists who trained animals using operant conditioning in applied settings.

What did the Brelands discover?

Instinctive behavior can interfere with learned behavior.

What is instinctual drift?

The gradual return of innate behavior that disrupts conditioning.

What did instinctual drift challenge?

The idea that animals are blank slates and all behavior can be equally conditioned.

What is the preparedness continuum?

The idea that some associations are biologically easier to learn than others.

What is behavioral genetics?

The study of genetic and environmental influences on behavior.

Who was Thomas Bouchard?

A researcher who studied identical twins raised apart.

What did Bouchard find?

Identical twins show strong similarities in intelligence and personality even when raised apart.

What is the effect of shared environment?

It has relatively little influence on personality differences.

What is nonshared environment?

Unique individual experiences that strongly shape personality.

What is heritability?

The proportion of variation in a trait in a population due to genetic differences.

What is an important limitation of heritability?

It does not mean a trait is fixed or unchangeable.