Psychology 101 The Birth of Psychology - Amazon S3...New science of psychology became organized into different branches, or schools of thought, ... Evolutionary psychology : study

Psychology 101 The Birth of Psychology: -In 1879, Wilhelm Wundt (1832-1920) established psychology in a lab in Germany -Defined psychology as “science of mental life” -Measured the time lag between people’s hearing a ball hit a platform and their pressing a telegraph key -Sought to measure “atoms of the mind”- the fastest & simplest mental processes -Added 2 key elements to enhance scientific nature of psychology, carefully measured observations and experiments ✳New science of psychology became organized into different branches, or schools of thought, including structuralism & functionalism Structuralism: -Edward Bradford Titchener, who was mentored by Wundt, aimed to discover the mind’s structure -Both Wundt & Titchener wanted to study the structure of consciousness through introspection

-During introspection, people were trained to report on sensations and other elements of experience in reaction to stimuli -Introspection relied on “self report” data, & introspective reports were used to build a view of the mind’s structure

-Introspection failed because people’s self-reports varied, depending on the experience & the person’s intelligence and verbal ability Functionalism: -William James (1842-1910) studied human thoughts, feelings, and behaviors, asking what functions might they serve? How might they have helped our ancestors survive?

➝Smelling is what the nose does, and thinking is what the brain does. But why? ➝Under the influence of evolutionary theorist Charles Darwin, James assumed that thinking, like smelling, developed because it was adaptive (contributed to our ancestors survival)

-Functionalism explored how mental and behavioral processes function, how they enable the organism to adapt, survive, and flourish -Consciousness function: enables us to consider our past, adjust to our present, & plan our future -James authored Principles of Psychology First Women in Psychology -Mary Whiton Calkins was a student in James’ graduate seminar & became the first female president of the American Psychological Association -Margaret Floy Washburn was the first female psychologist PhD/2nd female president of APA

✳Sigmund Freud concentrated on how the unconscious mind affects the development of one’s personality

-Believed that our conscious experiences were only the tip of the iceberg, that beneath the surface are primitive biological urges that are in conflict with the requirements of society and morality -These unconscious motivations and conflicts are responsible for much of human behavior and many medically unexplainable physical symptoms that troubled his patients

✳Freud believed we were driven by 2 engines: Sex & aggression (pessimistic view) ✳He also suggested that many of the things that occur in childhood shape our personality and account for our later behavior ✳He devised a way of treating patients with a method of free association

-He encouraged them to say whatever came into their minds, not to edit or censor their thoughts

✳Freud’s role, that of a psychoanalyst, was to be objective (just sat & listened, then interpreted) -He believed free association revealed the operation of the unconscious mind

✳Freud believed that dream analysis was an important psychological tool because dreams were expressions of the most primitive unconscious urges ✳Psychoanalysis- a method of treating mental illness that analyzes information contained in the unconscious mind

-Takes 20 to 30 sessions to be analyzed, need your doctor to take you to your basement (hidden problems) -Only rich people could afford it

-Came up with brief psychoanalysis: psychodynamics (less about sex) Behaviorism: ✳Behaviorism: defined psychology as “scientific study of observable behavior” WITHOUT reference to mental processes -John B. Watson (classical conditioning) and B.F. Skinner (operant conditioning) dismissed introspection and redefined psychology

-They said science is rooted in observation: what you cannot observe and measure you cannot scientifically study

-Became a major force in psychology into 1960’s -Watson and Rosalie Rayner conducted famous “Little Albert” experiments

-All about learning; how we learn observable responses -Best for children -Phobia: irrational fear of something that wouldn’t normally be deemed fearful -If you learn to be afraid, you can unlearn your fear

Humanistic Psychology: -Rogers and Maslow found Freudian psychology & behaviorism too limiting -Opposition to Freud: they wanted to be optimistic & thought he gave too much credit to our unconscious mind, believing that we can control our body

-You are in charge of your body, help you help yourself -All about self: self control, self respect, self actualization Cognitive Psychology ✳Most dominant today -This cognitive revolution led the field back to its origin of consciousness

-Everything is about THINKING -It scientifically explores the ways we perceive, process, and remember information

-They show statistics (e.g. if you’re afraid of flights, they say hey you're more likely to get in car crash)

-Cognitive neuroscience was birthed by the marriage of cognitive psychology (science of the mind) and neuroscience (science of the brain) Modern Definition of Psychology -Psychology: the science of behavior and mental processes -Behavior: anything an organism does (any action we can observe and record) -Mental processes: the internal, subjunctive experiences we infer from behavior (sensations, perceptions, dreams, thoughts, beliefs & feelings) -Psychology is less a set of findings than a way of asking and answering questions -Psychology is growing & globalizing Evolutionary Psychology & Behavior Genetics ✳Nature Nurture issue: longstanding controversy over the relative contributions that genes and experience make to the development of psychological traits and behaviors

-Today’s science sees traits and behaviors arising from the interaction of nature & nurture -Charles Darwin proposed the evolutionary process of natural selection, which is the principal that among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed on to succeeding generations ✳Evolutionary psychology: study of the evolution of behavior and the mind, using principles of natural selection ✳Behavior genetics: study of the relative power and limits of genetic and environmental influences on behavior ✳Culture: shared ideas and behaviors that one generation passes on to the next

-Culture shapes behavior

-Even when specific attitudes & behaviors vary by gender or across cultures, the underlying causes are much the same

✳Positive psychology: the scientific study of human functioning, with the goals of discovering and promoting strengths and virtues that help individuals and communities to thrive Levels of Analysis- the differing complementary views, from biological to psychological to socio-cultural, for analyzing any given phenomenon Biopsychological approach: viewpoint that incorporates various levels of analysis and offers a more complete picture of any given behavior or mental process Psychology’s subfields are united by a common quest: describing and explaining behavior and the mind underlying it -Some psychologists conduct basic research that builds psychology’s knowledge basis -Some may conduct applied research, the scientific study that aims to solve practical problems Branches of Psychology Counseling Psychology: branch of psychology that assists people with problems in living (school, work, marriage) and in achieving greater well being Clinical Psychology: branch of psychology that studies, assesses, and treats people with psychological disorders Psychiatry: a branch of medicine dealing with psychological disorders that is practiced by physicians who sometimes provide medical treatments as well as psychological therapy Community Psychology: branch of psychology that studies how people interact with their social environments and how social institutions affect individuals and groups Testing effect: enhanced memory after retrieving, rather than simply rereading, information SQ3R: study method that is an acronym for survey, question, read, retrieve, review Intuition- effortless, immediate, automatic feeling or thought Hindsight Bias- tendency to believe, after learning an outcome, that one would have forseen it (AKA I-knew-it-along phenomenon) ✳hindsight bias, overconfidence, and our tendency to perceive patterns in random events often lead us to overestimate our intuition -Putting a scientific attitude into practice requires not only curiosity and skepticism, but also humility (an awareness of our own vulnerability to error and an openness to surprises and new perspectives)

-Critical Thinking: thinking that does not blindly accept arguments and conclusions, but rather examines assumptions, appraises the source, discerns hidden values, evaluates evidence, and assesses conclusions The Scientific Method -Scientific method: a self-correcting process for evaluating ideas with observation and analysis ✳Theory: explanation using an integrated set of principles that organizes observations and predicts behavior or events ✳Hypothesis: testable prediction, often implied by a theory ✳Operational definition: carefully worded statement of the exact procedures (operations) used in a research study ✳Replication: repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding extends to other participants and circumstances ✳The starting point of any science is DESCRIPTION -Descriptive methods (describe behaviors):

1) Case studies (in-depth analyses of individuals or groups) a) Case studies involve only one individual or group, so we can’t know for sure

whether the principles observes would apply to a larger population 2) Naturalistic observations (watching and recording the natural behavior of many

individuals) a) Does NOT explain behavior, but describes it

3) Surveys and interviews (asking people questions) a) Subtle changes in the order or wording of questions can have major effects b) Population: all those in a group being studied, from which samples may be drawn c) Random sample: sample that fairly represents a population because each member

has an equal chance of inclusion -Correlational Methods (associate different factors)

-Correlation: a measure of the extent to which 2 factors vary together, and thus of how well either factor predicts the other -Correlation coefficient: a statistical index of the relationship between two things (from -1.00 to +1.00) ✳CORRELATION DOES NOT PROVE CAUSATION; IT INDICATED THE POSSIBILITY OF A CAUSE-EFFECT RELATIONSHIP BUT DOES NOT PROVE SUCH

-Experimental group: people receive the treatment

-Control group: does not receive the treatment -Double blind procedure: experimental procedure in which both the research participants and the research staff are ignorant about whether the research participants have received the treatment or a placebo -Experiments aim to manipulate an independent variable, measure a dependent variable, and to control confounding variables

-Independent variable: the factor in an experiment that is manipulated; the variable whose effect is being studied -Confounding variable: the factor in an experiment other than the independent variable that might produce an effect -Dependent variable: the outcome that is measured in an experiment; the variable that may change when the independent variable is manipulated

✳Psychological science focuses less on particular behaviors than on seeking general principles that help explain many behaviors ✳Ethics Codes of the APA urge researchers to:

1) Obtain potential participants informed consent before the experiment 2) Protect them from harm and discomfort 3) Keep information about individual participants confidential 4) Fully debrief people (explain the research afterward)

The Biology of the Mind -German physician Franz Gall proposed that phrenology, studying bumps on the skull, could reveal a person’s mental abilities & character traits

-Despite initial acceptance of Gall’s speculations, bumps on the skull tell us nothing about the brain’s underlying functions -However, phrenology did focus attention on the localization of function (the idea that various brain regions have particular functions) -Though they are not the functions Gall proposed, different parts of the brain do control different aspects of behavior

-Biological perspective: concerned with the links between biology and behavior (biological activity & psychological events)

-Includes psychologists working in neuroscience, behavior genetics, and evolutionary psychology -These researchers may call themselves behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, or biopsychologists

✳We are biopsychosocial systems: our cells make up tissues that make up organs that make up organ systems that are part of an individual, and the individual is part of a family, culture, & community

-To understand our behavior we need to study how these biological, psychological, and social systems work and interact

Neural Communication: ✳Neuron- nerve cells; the building blocks of the human nervous system; each consists of a cell body (the cell’s life support center) and its branching fibers

-DENDRITES LISTEN, AXONS SPEAK -Unlike the short dendrites, axons may be very long, projecting several feet through the body -Some axons are encased in a myelin sheath, a layer of fatty tissue that insulates them and speeds their impulses -As myelin is laid down up to about age 25, neural efficiency, judgement, and self- control grow

-If the myelin sheath degenerates, multiple sclerosis results; communication to muscle slows, with eventual loss of muscle control

✳Glial Cells- cells in the nervous system that support, nourish, and protect neurons; may also play a role in learning, thinking, and memory

The Neural Impulse -Neurons transmit messages when stimulated by signals from our senses or when triggered by chemical signals from neighboring neurons -In response, a neuron fires an impulse called the ACTION POTENTIAL (a brief electrical charge that travels down its axon) -Neurons generate electricity from chemical events

-In the neuron’s chemistry-to-electricity process, ions are exchanged

-The fluid outside an axon’s membrane has mostly positive charged sodium ions -A resting axon’s fluid interior has mostly negatively charged ions ✳This positive-outside/negative-inside state is called the RESTING POTENTIAL

-The axon’s surface is selectively permeable -When a neuron fires, the first section of the axon opens its gates and positively charged Na+ flood in

-The loss of the inside/outside charge difference, called DEPOLARIZATION, causes the next axon channel to open and then the next (like dominos) -This temporary inflow of positive ions is the neural impulse (the action potential) -During a resting pause called the REFRACTORY PERIOD, the neuron pumps the positively charged sodium ions back outside and then it can fire again

Each neuron is a decision making device performing complex calculations as it receives signals from other neurons

-Most signals are excitatory, somewhat like pushing a neuron’s accelerator -Some are inhibitory, like pushing it’s brake -If excitatory signals exceed the inhibitory signals by a minimum intensity, or THRESHOLD, the combined signals trigger an action potential

-Increasing the level of stimulation above the threshold will NOT increase the neural impulse’s intensity

-Neuron’s reaction is an ALL OR NONE RESPONSE (either fires or doesn’t) -A strong stimulus can trigger more neurons to fire, and to fire more often, but it does not affect the action potential’s strength or speed

How Neurons Communicate -Sir Charles Sherrington discovered neurons had synapses and weren’t uninterrupted

-Synapse: the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron; tiny gap is called the synaptic gap or cleft

-The synaptic cleft is less than a millionth of an inch wide -When an action potential reaches the terminals at an axon’s end, it triggers the release of chemical messengers called neurotransmitters

-Within 1/10,000th of a second, the neurotransmitter molecules cross the synaptic cleft and bind to receptor sites on the receiving neuron

-The neurotransmitter unlocks tiny channels at the receiving site, and electrically charged atoms flow in, exciting or inhibiting the receiving neuron’s readiness to fire -Excess neurotransmitters drift away, are broken down by enzymes, or are reabsorbed by the sending neuron in a process called REUPTAKE How Neurotransmitter Influence Us -Neurotransmitter systems do not operate in isolation; they interact, and their effects vary with the receptors they stimulate

-Acetylcholine(ACh): neurotransmitter that plays a role in learning and memory -Messenger at every junction between motor neurons (which carry information from the brain and the spinal cord to the body’s tissues) & skeletal muscles -When ACh is released to our muscle cell receptors, the muscle contracts -If ACh transmission is blocked, the muscles cannot contract & we are paralyzed

-Endorphin: naturally occurring opiates -Neurotransmitters linked to pain control & pleasure

How drugs and Other Chemicals Alter Neurotransmission: -When flooded with opiate drugs such as heroin, morphine, & codine, the brain, to maintain its chemical balance, may stop producing its own natural opiates -When the drug is withdrawn, the brain then may be deprived of any form of opiate, causing intense discomfort -Agonist: molecule that increases a neurotransmitter’s actions

1) May increase the production or release of neurotransmitter 2) May block reuptake in the synapse 3) May be similar enough to the neurotransmitter to bind to its receptor and mimic its

excitatory or inhibitory effects -Antagonist: molecule that decreases a neurotransmitter’s action by blocking production or release (ex:botox)

-Antagonists are enough like the natural neurotransmitter to occupy its receptor site and block its effect, but not similar enough to stimulate the receptor)

The Nervous System (the body’s electrochemical communication network): ✳Nervous system divides into:

1) Central Nervous System: brain and spinal cord; the body’s decision maker 2) Peripheral Nervous System: the sensory and motor neurons responsible for gathering

information and for transmitting CNS decisions to other body parts -Nerves: electrical cables formed of bundles of axons that link the CNS with the body’s sensory receptors, muscles, and glands -Information travels in the nervous system through 3 types of neurons:

1) Sensory Neurons: carry messages from the body’s tissues and sensory receptors inward (afferent)

2) Motor Neurons: carry instructions from the CNS out to the body’s muscles and glands (efferent)

3) Interneurons: neurons within the brain and spinal cord; communicate internally and process information between the sensory inputs and motor outputs

The Peripheral Nervous System

1) Somatic Nervous System: enables voluntary control of our skeletal muscles

2) Autonomic Nervous System: controls our glands and our internal organ muscles, thus influencing glandular activity, heartbeat, and digestion

a) Autonomic means self-regulating ✳Autonomic nervous system subdivisions: ➝ SNS & PSNS work together to keep us in a steady internal state of homeostasis

1) Sympathetic Nervous System- arouses the body, mobilizing its energy 2) Parasympathetic Nervous System: calms the body, conserving its energy

The Central Nervous System ✳The brain: neurons cluster into work groups called neural networks ✳The spinal cord: a two-way information highway connecting the PNS and the brain

-Reflexes: our automatic responses to stimuli -The neural pathways governing our reflexes illustrate the spinal cords work

The Endocrine System: ✳Both the nervous and endocrine systems are systems of communication:

1) Nervous-electrochemical -Quick action and reaction

2) Endocrine-chemical -Slow communication system that secretes hormones into the bloodstream

✳Hormones: chemical messengers that are manufactured by the endocrine glands, that travel through the bloodstream, and affect other tissues, including the brain

➝When hormones act on the brain, they influence our interest in sex, food, & aggression -Both the endocrine system and the nervous system produce molecules that act on receptors elsewhere -In a moment of danger, the ANS orders the adrenal glands (on top of the kidneys) to release epinephrine and norepinephrine (also called adrenaline & nonadrenaline)

-These hormones increase heart rate, blood pressure, and blood sugar, providing a surge of energy

-The most influential endocrine gland is the pituitary gland, a pea sized structure located in the core of the brain, where it is controlled by an adjacent brain area, the hypothalmus

-Among the hormones released by the pituitary is a growth hormone that stimulates physical development

-Another is oxytocin, which enables contractions associated with birthing, milk flow during nursing, and orgasm (also promotes pair bonding and social trust)

✳Brain(hypothalmus)➝pituitary➝other glands➝hormones➝body and brain ]The Tools of Discovery ✳Scientists can selectively destroy (lesion) or electrically, chemically, or magnetically stimulate the brain

-EEG-Electroencephalogram: an amplified readout of waves produced by the electrical activity in the brain’s neurons sweeping in a wave across its surface measured by electrodes placed on the scalp -PET-Positron emission tomography: depicts brain activity by showing each brain area’s consumptions of its chemical fuel, the sugar glucose -MRI-Magnetic resonance imaging: uses magnetic fields and radio waves to produce computer-generated images of soft tissue (show brain anatomy) -fMRI- Functional MRI: can reveal the brain’s functioning as well its structure -CAT-computerized autotomography:

Structure of the Brain ✳Brainstem: oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull

-Responsible for automatic survival functions -The slight swelling the medulla (the base of the brainstem that controls heartbeat and breathing) -Just above the medulla sits the pons (helps coordinate movement and control sleep)

✳Thalamus: sits above the brainstem; a pair of egg-shaped structures that act as the brain’s sensory control center

-Receives information from all the senses except smell and routes it to the higher brain regions that deal with seeing, hearing, tasting, and touching

✳The Reticular Formation: located inside the brainstem and between your ears -A neuron network extending from the spinal cord right up through the thalamus -As the spinal cord’s sensory input flows up to the thalamus, some of it travels through the reticular formation, which filters incoming stimuli, relays important information to other brain areas, and controls arousal

✳The Cerebellum: along with the basal ganglia (deep brain structures involved in motor movement) enables nonverbal learning and skill memory

-Also helps us judge time, modulate our emotions, and discriminate sounds and textures The Limbic System: -Sits between the brain’s older parts and its cerebral hemispheres (2 halves) -This system contains the amygdala, the hypothalamus, and the hippocampus

1) The Hippocampus: processes conscious, explicit memories 2) Amygdala: linked to aggression and fear 3) Hypothalamus: located just below the the thalamus; directs several maintenance activities

(eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and award

a) Help maintain a steady homeostatic internal state The Cerebral Cortex & Our Divided Brain ✳Cerebral Cortex: intricate fabric of interconnected neural cells covering the cerebral hemispheres; the body’s ultimate control and information-processing center

-What makes us distinctively human mostly arises from the complex functions of our cerebral cortex

-Structure of the cortex: -Each hemisphere’s cortex is subdivided into four lobes, separated by fissures (or folds)

1) Frontal 2) Parietal 3) Occipital 4) Temporal

-Functions of the cortex -Motor Cortex: an area at the rear of the frontal lobes that controls voluntary movements

-Discovered by Fritsch and Hitzig -Foerster and Penfield discovered that body areas requiring precise control, such as the fingers and the mouth, occupy the greatest amount of cortical space -Cognitive neural prothesthics

Somatosensory cortex: specializes in receiving information from the skin senses and from the movement of body parts

-The more sensitive the body region, the larger the somatosensory cortex area devoted to it

Visual cortex in occipital lobes receives input from your eyes Auditory cortex in temporal lobes receives input from your ears

-MRI scans of people with schizophrenia have revealed auditory areas in the temporal lobe during the false sensory experiene of auditory hallucinations

Association areas: areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking

-Found in all four lobes The Brain’s Plasticity -Plasticity: the brain’s ability to modify itself after damage -Some brain-damage effects can be traced to two hard facts:

1) Severed brain and spinal cord neurons usually do not regenerate 2) Some brain functions seem preassigned to specific areas

-However, some neural tissue can reorganize in response to damage -Constraint induced therapy: aims to rewire brains and improve the dexterity of a brain damages child or even an adult stroke victim -Blindness or deafness makes their unused brain areas available for other uses -Neurogenesis: when the brain attempts to mend itself by producing new brain cells The Divided Brain ✳Vogel and Bogen speculated that major epileptic seizures were caused by an amplification of abnormal brain activity bouncing back and forth between the two cerebral hemispheres -Corpus callosum: wide band of axon fibers that connects left brain and right brain & carries messages between them -Vogel & Bogen wondered if they could put an end to seizures by severing the corpus callosum

-Surgeons operated and the seizures stopped -Split Brain: condition resulting from surgery that isolates the brain’s two hemispheres by cutting the fibers (mainly those of the corpus callosum) connecting them Left brain-speech and comprehension Right brain-spacial intelligence (shapes architecture etc) Left brain controls movement of right side; right brain controls movement of left Psychoactive drugs: chemicals that change perception and mood The severity of substance use disorder varied from mild (2 to 3 indicators), to moderate (four to five indicators), to severe (6 or more indicators) Tolerance: with repeated use, the desired effect requires larger doses Addiction: compulsive craving of drugs or certain behaviors such as gambling despite known harmful consequences Withdrawal: discomfort and distress that follow discontinuing an addictive drug or behavior 3 major categories of psychoactive drugs: depressants, stimulants, and hallucinogens

Depressants: calm neural activity and slow body functions Stimulant: excites neural activity and speeds up body functions; can be addictive Hallucinogens: distort perceptions and evoke sensory images in the absence of sensory input Drug & types

Depressant Stimulant Hallucinogens

Alcohol Caffeine LSD- synthetic

Opiates (heroin, codeine, and morphine)

Nicotine MDMA (Ecstasy)- synthetic

Barbiturates (tranquilizers) Cocaine Marijuana-natural

Amphetamines

Meth

Ecstasy

BEHAVIOR GENETICS: PREDICTING INDIVIDUAL DIFFERENCES -Behavior genetics: the study of the relative power and limits of genetic and environmental influences on behavior -Environment: every nongenetic influence, from prenatal nutrition to the people and things around us ✳GENES: OUR CODES FOR LIFE: -Chromosomes: threadlike structures made of DNA molecules that contain the genes (we have 46 chromosomes) -DNA: a complex molecule containing the genetic information that makes up the chromosomes -Genes: the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins

-You have 20,000-25,000 genes, which are either active (expressed) or inactive -Environmental events turn on genes; when turned on, genes provide the code for creating protein molecules, our body’s building blocks -Genome: the complete instructions for making an organism, consisting of all the genetic material in that organism’s chromosomes -We are 96% identical to chimpanzees -Our genes help explain both our shared human nature and our human diversity ✳TWIN & ADOPTION STUDIES:

-Identical (monozygotic) twins: develop from a single fertilized egg that splits in two, creating two genetically identical organisms

-Although identical twins have the same genes, they don’t always have the same number of copies of those genes; this variation explains why one twin may have a greater risk for certain illnesses and disorders -Most identical twins share a placenta during prenatal development, but ⅓ sets of twins have separate placentas; one twins placenta may provide slightly better nourishment, which may contribute to identical twin differences

-Fraternal (dizygotic) twins:develop from separate fertilized eggs; they are genetically no closer than ordinary brothers and sisters, but they share a prenatal environment -Identical twins raised apart have similarities of tastes, physical attributes, personality, abilities, attitudes, interests, and even fears -Genetic relatives: biological parents and siblings -Environmental relatives: adoptive parents and siblings -People who grow up together, whether biologically related or not, do not much resemble one another in personality; however, parents do influence their children’s attitudes, values, manners, politics, and faith -7 in 8 adopted children have reported feeling strongly attached to or both adoptive parents ✳TEMPERAMENT & HEREDITY: -Temperament: a person’s characteristic emotional reactivity and intensity -Temperament is quickly apparent after birth and genetically influenced -Some babies are difficult, some are easy, some are slow to warm up -Temperament differences typically persist -Identical twins, more than fraternal twins, often have similar temperaments -The genetic effect appears in physiological difference; anxious, inhibited infants have high and variable heart rates and a reactive nervous system; when facing new situations, they become more physiologically aroused

-One form of a gene that regulates the neurotransmitter serotonin predisposes a fearful temperament and, in combination with unsupportive caregiving, an emotionally reactive child

✳HERITABILITY: -Heritability: the proportion of variation among individuals that we can attribute to genes

-The heritability of a trait may vary, depending on the range of populations and environments studied

-The heritability of general intelligence is 66%; this does NOT mean that your intelligence is 66% genetic, but rather that genetic influence explains about 66% of the observed variation among people -We can NEVER say what percentage of an individual’s personality or intelligence is inherited