Nature vs. Nurture in Psychology

Nature vs. Nurture

• Psychology aims to differentiate between nature (genetics) and nurture (environment).

Nature

• Encompasses genetics, influencing who and what we are from within.
• Noam Chomsky states genetic factors differentiate humans from animals.
• Genetics consist of universal grammar affecting speech.

Nurture

• Includes environment, learning, and conditioning that shape our behaviors through rewards or punishments.
• John B. Watson believed that with a dozen healthy infants, he could shape their lives regardless of talents or ancestry.

Nature and Nurture

• Nature and nurture interact to shape individuals.
• Nature determines eye and hair color, body shape, sex, and temperament.
• Nurture determines culture, social groups, norms, and family influences.

Epigenetics

• Explores the interactions between nature and nurture.

Rat Studies

• Rat licking studies show how a genetic component changes with the mother's licking intensity as the behavior is passed to offspring.
• Rat memory studies found that enriched environments enhance LTP (long-term potentiation), which in turn improves memory.
• Offspring in rat memory studies mirrored same LTP enhancement.

Twin Studies

• Identical twins share the same DNA and sex, originating from a monozygotic egg.
• Fraternal twins have different DNA, are not more genetically similar than siblings, may have different sexes, and come from dizygotic eggs.
• Minnesota twin studies found that twins reared apart share many similarities, based on 35 years of research.
• The Jim twin study showed uncanny similarities between twins, including marrying and divorcing women with the same names, naming sons and dogs similarly, and having similar jobs and vacations.

Types of Studies

• Family, DNA, twin, and adoption studies are used in these fields.

Heritability

• Heritability is the amount of variation among individuals that can be attributed to genetics.
• There are nine pairs of traits that are highly hereditary; identical twins share more of these traits than non-identical twins.
• 62% of differences in academic performances are linked to genetic factors.

Nervous System

• The peripheral nervous system lies outside the brain and spine areas.
• The central nervous system consists of the brain and spinal cord.
• Any activity utilizes both nervous systems.
• Somatic nervous system communicates sensory information via sensory neurons to the centra nervous system.
• The autonomic nervous system regulates involuntary functions.
• The sympathetic nervous system triggers fight or flight responses, increasing heart rate, blood pressure, and respiration.
• The parasympathetic nervous system calms the body after a fight or flight response, working opposite the sympathetic nervous system.

Psychology Myths

• Common psychology myths include the beliefs that we only use 10% of our brain, that we cannot grow new neurons, and that individuals are either left-brained or right-brained.

Brain

• Hans Berger used an EEG machine ~100 years ago to observe electrical pulses made by neurons.
• There are ~900 billion glial cells, once thought of as helper cells that do not show up on EEGs, that send chemical signals to other neurons.
• The neural system facilitates thoughts, understanding, inspiration, and insight.

Neurons

• Sensory neurons respond to non-chemical stimulations, with different neurons for each sense, and send afferent signals to the brain.
• Motor neurons connect to muscles, enabling both voluntary and involuntary movements, and send efferent signals exiting the brain.
• S.A.M.E. stands for Sensory Afferent Motor Efferent.
• Neurons are the building blocks of the nervous system, exhibiting great specificity.
• Neurons receive, carry, and send messages.
• Cells firing in specific patterns leads to thoughts.

Neuron Parts

• The parts of a neuron are dendrites, soma, nucleus, myelin sheath, axon, axon terminal, and terminal buttons.

Myelin Sheath

• The myelin sheath is a fatty substance protecting most neurons in the brain, insulating the axon for faster nerve impulse transmission.
• Many disorders are linked to myelin sheath deterioration.

Synapses

• After each terminal button there is a synapse or synaptic gap.
• Neurotransmitters cross the synaptic gap and bind to the postsynaptic neuron's dendrites.

Neural Firing

• Neural firing progresses from dendrites to soma, then axon, and finally to terminal buttons (DSAT).
• Neurons fire when there is a shift in electrical energy, creating an action potential.

Action Potential

• An action potential is electrical impulse traveling down the axon.
• When action potential reaches the terminal buttons, neurotransmitters are released into the synapse and bind to the next neuron's dendrites.
• Neurotransmitters are either excitatory (more likely to fire the next neuron) or inhibitory (less likely to fire the next neuron).
• Neurotransmitters are encased in axon terminals.
• Resting potential is -70 millivolts with a polarized charge (positive outside).
• Firing threshold refers to number of neurotransmitters needed for firing.
• All or none law states once the threshold is reached, neuron will fire with the same intensity every time.
• Once fired, an electrical impulse travels down axon, polarity changes to +30mV inside neuron, also known as depolarization.
• The refractory period is when the neuron cannot fire again.
• Reuptake is the process of the sending neuron re-collecting released neurotransmitters.
• Neurotransmitters significantly influence cognition and behavior.
• Neurotransmitters are chemical messengers of the nervous system with different impacts on thinking and behavior; they can be exhibitory or inhibitory.

Neurotransmitters Cont.

• Glutamate is the most abundant exhibitory neurotransmitter that strengthens memory skills and learning.
• GABA (Gamma-aminobutyric acid) is the most abundant inhibitory neurotransmitter, associated with anxiety-related disorders.
• AcH (acetylcholine) is required for movement and involved in memory and learning; diminished function is connected with Alzheimer's.
• Dopamine relates to pleasure and reward, as well as movement, attention, and learning.
• Lack of dopamine relates to Parkinson's disease, and excess dopamine relates to schizophrenia.
• Endorphins are the body's natural painkillers, elevated by long and extreme exercise to create a euphoric feeling.
• Epinephrine or Adrenaline acts as both a neurotransmitter and hormone, boosting energy in fight or flight responses.
• Norepinephrine or Noradrenaline enhances arousal, alertness, and vigilance.
• Serotonin plays a role in mood, appetite, sleep, and dreams.

Psychoactive Drugs

• Psychoactive drugs and other substances directly impact neurotransmitters at the synapse, acting as agonists or antagonists.
• Agonists enhance neural transmitter actions in two ways: Direct agonists mimic neurotransmitters and bind to the next neuron's receptors, and indirect agonists block reuptake of neurotransmitters, also known as reuptake inhibitors.
• Heroin is a direct agonist for endorphins, mimicking them so that receptor sites cannot distinguish between them and the chemical structure of heroin.
• Nicotine acts as an ACh agonist, stimulating skeletal muscles and increasing heart rate.
• Black widow venom is a toxin acting as an acetylcholine agonist, causing continuous ACh release at neuromuscular junctions.
• Prozac inhibits serotonin reuptake, flooding the synapse with serotonin.
• Cocaine inhibits dopamine reuptake, flooding the synapse with dopamine.

Antagonists

• Antagonists inhibit neurotransmitter actions, binding to receptors but not stimulating them.
• An antagonist blocks a neurotransmitter from being released or binding to the receptor site.
• Botox prevents ACh neurotransmitters from reaching receptors, affecting muscle movement.
• Thorazine is an antagonist for dopamine, blocking dopamine receptors and inhibiting transmission of dopamine.

Psychoactive Drug Commonalities

• Psychoactive drugs alter mental states and activate dopamine-producing neurons in the brain's reward system.
• Increased dopamine from psychoactive drugs is associated with reward, leading to a stronger desire to take the drug again.
• Many psychoactive drugs create tolerance, requiring increased amounts to achieve the original effect.
• Many psychoactive drugs cause physical dependence, potentially requiring administration to prevent withdrawal symptoms.
• Most psychoactive drugs affect specific neurotransmitters.
• The blood-brain barrier only allows certain chemicals from the blood to enter the brain.

Types of Psychoactive Drugs

• Depressants slow or inhibit central nervous system functions, causing drowsiness, sedation, relieving anxiety, and lowering inhibition; deadly when combined.
• Alcohol, the second most used drug in the US, is a GABA agonist that lessens inhibition by depressing brain centers responsible for judgment and self-control.
• Opioids, agonists for endorphins like heroin, oxycodone, and fentanyl, are incredibly addictive and trigger powerful withdrawal symptoms.
• Stimulants activate the sympathetic nervous system, increase brain activity, arousal, behavior, and mental alertness.
• Caffeine is the most used drug, promoting wakefulness, mental alertness, and faster thought processing by stimulating dopamine release and blocking adenosine.
• Caffeine is physically addictive and causes withdrawal symptoms.
• Cocaine is a dopamine agonist, which elevates serotonin and norepinephrine, heightens confidence, and results in an intense euphoria.
• Cocaine also is highly addictive and produces a crash when its effects dissipate.
• Hallucinogens create sensory and perceptual distortions, alter moods, and affect thinking, with research ongoing for therapeutic uses.
• THC is a mild hallucinogen producing mild euphoria and relaxation.THC interferes with muscle coordination, learning, memory, and overall cognitive function, but has various therapeutic applications.

Hindbrain

• The hindbrain contains the medulla, pons, and reticular activating system.
• The medulla handles basic autonomic functions, including heart rate, breathing, blood pressure, and reflexes like swallowing, sneezing, and vomiting.
• The reticular activating system (RAS) is a nerve fiber network involved in attention, arousal, and alertness.
• The pons bridges to the brain system, aids the cerebellum to coordinate and integrate movements on each side of the body, and plays a role in sleep functions.

Midbrain

• The midbrain is the nerve system connecting higher and lower brain portions, relaying information between the brain, eyes, and ears.

Limbic System

• The limbic system involves emotion, motivation, learning, and memory.
• The limbic system structure includes the thalamus, hypothalamus, amygdala, and hippocampus.
• The thalamus is a sensory switchboard, sorting and sending sensory information to the cortex for interpretation.
• The hypothalamus controls fight or flight responses, feeding, and sexual motivation.
• The amygdala supports anger, aggression, and fear, helping to ingrain highly emotional memories.
• The hippocampus converts short-term memory to long-term memory, processes and retrieves declarative memories and spatial relationships, and its dysfunction can lead to Alzheimer's and anterograde amnesia.

Brain Hemispheres and Lobes

• The brain has two hemispheres, each containing four lobes: frontal, parietal, occipital, and temporal.

Frontal Lobe

• The prefrontal cortex facilitates cognitive functions like thinking, planning, decision-making, and impulse control.
• The prefrontal cortex undergoes substantial reorganization from 18 to 25 years old.
• The motor cortex initiates voluntary movements contralaterally, wherein the left hemisphere controls the right side of the body and vice versa; body areas facilitating diverse and precise movements have more tissue on this strip.

Parietal Lobe

• The somatosensory cortex represents touch sensations contralaterally; more sensitive body parts have more tissue devoted to them on this strip.

Occipital Lobe

• The primary visual cortex connects to the eyes; dysfunction can cause blindness.

Temporal Lobe

• The primary auditory cortex is where auditory perception occurs.
• The auditory association cortex helps differentiate and associate sounds.

Language

• Language is lateralized to the left side.
• Broca's area, in the frontal lobe, controls speech expression; injuries due to stroke can lead to Broca's aphasia.
• Wernicke's area, in the temporal lobe, is involved in language understanding; damage causes Wernicke's aphasia.