1) Multiple Genes, Environment, Profiling, and Biases

Who was Ronald Cotton

A man wrongly convicted of rape in 1987 based on eyewitness testimony, later freed by DNA evidence in 1995

What does Ronald Cotton teach us

Eyewitness memory can be wrong; DNA evidence is far more reliable

About what percent of people on death row are later found innocent

Around 4.1%

What are polygenic traits

Traits controlled by many genes instead of just one

What are two examples of polygenic traits

Eye color (2–15 genes) and skin color (3+ genes)

What affects eye and skin color

The amount and distribution of melanin

What are quantitative traits

Traits affected by many genes and the environment, showing a wide range of outcomes (like height or weight)

What does the “mean” represent on a normal distribution curve

The average value (top/middle of the bell curve)

What does “variance” mean

How spread out the data is — how different people are for that trait

What does low variance mean

People look very similar; hard to tell apart (bad for eyewitness accuracy)

What is nature vs nurture

The debate about whether traits are caused by genes (nature) or environment (nurture)

What is heritability

he amount of variation in a trait (within a population) explained by genetic differences

How is heritability estimated

By comparing relatives (like parents and kids or siblings)

What does heritability tell us about individuals

Nothing directly — it describes populations, not individuals

Can we tell who’s a criminal by their appearance

No — studies show no physical differences between violent and nonviolent offenders

What does the Michigan study show

Face shape and size don’t predict criminal behavior

What did the mouse study teach us

Environment (like diet) can make groups look genetically different even when they’re not

What is epigenetics

The study of how environmental factors turn genes on or off without changing DNA

What happened in the Agouti mouse study

Mice fed special food had babies that were healthier and brown instead of yellow and obese

What does the Agouti mouse study show

The environment (diet) can change gene expression and pass those changes to offspring

What does it mean if a trait is “highly heritable”

It’s strongly influenced by genes — but still affected by environment

Does high heritability mean a trait is all genetic

No — environment still plays a big role

Why can’t heritability explain individual differences

Because it only applies to groups, not single people

What is implicit bias

Unconscious stereotypes or judgments that affect how we see others

How does implicit bias form

Through lifelong exposure to messages, experiences, and media

How can implicit bias affect justice

It can cause wrongful convictions if people “look” like a stereotype of a criminal

What is DNA profiling (DNA fingerprinting)

A test that uses DNA differences to identify people

How is DNA profiling used

To confirm or clear suspects by comparing crime scene DNA to a person’s DNA

Why is DNA profiling important

It’s helped free innocent people and catch real criminals

What group uses DNA profiling to help innocent prisoners

The Innocence Project

How many people has the Innocence Project helped free

About 350 innocent prisoners; also found 150 true perpetrators

What is the main takeaway about genes and environment

Most traits are a mix of both — genes give the potential, environment shapes the outcome