Unit 2

Nature vs. Nurture

Behavior is influenced by both genetic (nature) and environmental (nurture) factors; modern research focuses on how they interact rather than choosing one over the other.

Epigenetics

The study of changes in gene expression caused by environmental factors that do not alter the DNA sequence.

Heritability estimate (h²)

A statistic that indicates the proportion of variability in a trait within a population that is due to genetic differences.

Types of twins

Monozygotic (MZ, identical) and Dizygotic (DZ, fraternal) twins.

Twin studies

They show how much variability is due to genetics (h²), shared environment (ES), and non-shared environment (ENS).

MZ and DZ twins genetic difference

MZ twins share 100% of their genes; DZ twins share about 50%.

Behavioral genetics

The field that studies the role of genetics in animal (including human) behavior.

Sensation

The detection of physical stimuli.

Perception

The interpretation of those stimuli by the brain.

Primary sensory areas organization

They are organized topographically, meaning adjacent neurons correspond to adjacent sensory receptors.

Primary sensory cortices

Brain regions responsible for processing basic sensory input: Visual: occipital lobe (V1), Auditory: superior temporal gyrus (A1), Somatosensory: postcentral gyrus (S1), Olfactory: piriform cortex, Gustatory: insular cortex.

Association cortex

Brain areas involved in integrating sensory information and linking it to memory, emotion, and action.

Binding problem

The challenge of explaining how the brain combines features (color, shape, sound) into a unified perception.

Auditory pathway

Cochlea → cochlear nucleus → superior olivary complex → inferior colliculus → medial geniculate nucleus → auditory cortex.

Mechanoreceptors

Sensory receptors that respond to mechanical pressure or distortion (touch, pressure, vibration).

Main somatosensory pathways

Dorsal column-medial lemniscus (fine touch, proprioception) and spinothalamic tract (pain, temperature).

Homunculus

A distorted representation of the human body based on the amount of sensory or motor cortex devoted to each body part.

Brain areas in pain perception

Thalamus, somatosensory cortex, anterior cingulate cortex, and insula.

Chemical senses receptors

Taste: taste buds on the tongue; Smell: olfactory receptors in the nasal epithelium.

Asomatognosia

The loss of recognition or awareness of parts of one's own body.

Astereognosia

The inability to recognize objects by touch despite normal sensory function.

Ageusia

The loss of taste perception.

Anosmia

The loss of the sense of smell.

Language and handedness

Most right-handed individuals have left-hemisphere language dominance; left-handers may have more bilateral or right-sided language representation.

Cerebral lateralization

The specialization of brain functions in the left and right hemispheres.

Split-brain studies

The two hemispheres can operate independently, with the left hemisphere more involved in language and the right in spatial tasks.

Analytic-synthetic theory

Suggests the left hemisphere is analytical (logical, sequential) and the right is holistic (creative, intuitive).

Brain regions associated with language

Broca's area (speech production), Wernicke's area (comprehension), arcuate fasciculus (connects them), angular gyrus (reading/writing).

Aphasias

Language disorders caused by brain damage; includes Broca's (non-fluent) and Wernicke's (fluent) aphasia.

Wernicke-Geschwind model

A classical model outlining the brain regions involved in language comprehension and production.