Statistics and Biology of Mind - Quick Review

Descriptive vs Inferential Statistics

• Descriptive statistics: summarize data with a single or few numbers (central tendency and dispersion).
• Inferential statistics: determine whether results generalize to a population; involve probability and hypothesis testing.
• Key concepts: random assignment, independent variable, dependent variable, null hypothesis, statistical significance.
• Base rates and base-rate fallacy: consider base rates (e.g., vaccination rates) before drawing conclusions.
• Significance threshold: p<0.05 means results are unlikely under the null hypothesis.

Measures of Central Tendency

• Mean: $\bar{x}=\frac{1}{n}\sum<em>{i=1}^n x</em>i$
• Median: middle point of ordered data
• Mode: most frequently occurring value
• Choosing measure: mean for symmetric data; median often better for skewed income data; mode describes the most common value.

Measures of Variation

• Range: $Range = x<em>{max}-x</em>{min}$
• Standard deviation: $s=\sqrt{\frac{1}{n-1}\sum<em>{i=1}^n (x</em>i-\bar{x})^2}$
• Normal distribution: most scores near the center; use of the standard deviation to describe spread (e.g., ~68% within 1 SD, ~95% within 2 SD).
• Outliers: data points far from the center, can distort the mean.

Inferential Statistics & Experimental Design

• Random assignment: equalizes background variables across groups.
• Independent variable (IV): what we manipulate (e.g., violent vs. nonviolent TV).
• Dependent variable (DV): what we measure (e.g., aggression levels).
• Statistical significance: unlikely difference due to chance; threshold typically p<0.05.
• Example structure: two groups, compute group means and SD to assess if observed difference is real beyond chance.
• Generalization: larger, representative samples improve inference to the population.

The Basic Brain–Mind Link (Biological Psychology)

• Core idea: everything psychological has a biological basis; mind-brain are linked.
• Terminology: biological psychology, biopsychology, neuropsychology, physiological psychology, etc.
• Sapolsky view: behavior is shaped by genes, hormones, neural activity, daily experiences, and culture.
• Mind vs brain: mind refers to thoughts/feelings/intentions; brain is the biological substrate.
• Phrenology (historical): localized function idea was partly right (localization) but methods were wrong.
• Localization of function: certain brain areas specialize in certain functions; today studied via networks and plasticity.
• Neuroplasticity: brain changes with experience; pathways form or rewire with learning.
• Examples of plasticity: London taxi drivers show enlarged hippocampus; musicians show enlarged auditory cortex; asymmetries in some skills reflect specialized brain changes.
• Culture and emotion: brain activation patterns vary with cultural norms for emotional expression.

Neurons and Neurotransmission (Basic Unit of the Nervous System)

• Neuron structure: dendrites (receive), soma/cell body (DNA, metabolism), axon (transmit), axon terminals (synaptic transmission).
• Myelin sheath: insulation around the axon, increases transmission speed; glial cells provide support.
• Communication: electrical signal (action potential) travels down the axon; chemical signal crosses the synapse via neurotransmitters.
• Synapse: gap between neurons; neurotransmitters released from axon terminal to receptors on the next neuron.
• Key neurotransmitters: $\text{dopamine}, \text{serotonin}, \text{acetylcholine}, \text{glutamate}$ (examples; linked to mood, movement, learning, etc.).
• Reuptake: neurotransmitters recycled after release.
• Resting potential: about $-70\ \mathrm{mV}$; depolarization (ion flow) leads to action potential.
• Action potential: all-or-none event; either the signal is sent at full strength or not at all.
• Ions and channels: opening/closing ion channels changes charge; depolarization triggers the spike; refractory period resets.
• Transmission speed: neural signals are fast but slower than electrical conduction in wires; roughly hundreds of miles per hour.

How Neurons Create Thoughts and Memories

• Networks: thoughts/memories arise from large networks of interconnected neurons (connectionism).
• Synapses and plasticity underlie learning and memory formation.
• Symbols and language involve left-hemisphere language networks; some languages may shift activation patterns with learning.

Quick Concepts for Review

• Glial cells: support cells; outnumber neurons (~10:1 in some estimates) and contribute to signaling and maintenance.
• MS (multiple sclerosis): degeneration of myelin disrupts fast transmission.
• Localized vs distributed processing: both local specialization and network-based processing important.
• Neurochemistry and behavior: neurotransmitters influence mood, arousal, movement, and cognition; pharmacology can modify them (e.g., serotonin reuptake inhibitors for depression).

Core Takeaways (Last-Minute)

• Descriptive stats summarize data; inferential stats test generalization to populations.
• Central tendency (mean/median/mode) and variation (range/SD) describe distributions.
• Statistical significance (p < 0.05) indicates results unlikely due to chance, but not absolute proof.
• Brain biology explains behavior: structure, chemistry, and networks shape thoughts, feelings, and actions; experience changes the brain (neuroplasticity).
• Neurons communicate via electrical (action potential) and chemical (neurotransmitters) signals across synapses; this underlies all mental processes.