Experimental designs: the search for causal explanations
Independent variable (IV) –
· an attribute that is manipulated by the experimenter while other aspects of the study
are held constant
· Drug Y
· The outcome, response or attribute that changesas a consequence of variation in the
Experimental study examples:
Does independent variable cause the dependent variable? Does X cause Y?
What’s the most suitable method?
The problem with experimental study - The control you get and gain may lose validity in the real
What do you do once you have the data? Organize and summarize it.Averages and variability
(24 vs 25. They’re 2 means, but are they significantly different?)
Use statistics and probability to rule out the findings were due to chance.
Validity and reliability: Psychometrics
· Reliability (Consistency) – dismiss unreliable measures – i.e. drastic, unrealistic changes
· Are we truly measuring what we claim to be measuring?
· Is the SAT a measure of IQ or something else?
· Intelligence versus learning versus creativity
Chapter 3: Evolution and Genes
How did we get here? Principles of evolution
· All living structures and form chance (usually but not always gradually) over long periods of
· Evolution is “change over time in the frequency with which particular genes occur within a
· Genetic changes create new structures
· New structures create new species
· When does enough change validate a new species?
· It’s a species when breeding between two “different” ones do not create viable offspring.
· We’re most closely related to apes, not chimps! Chimps are the other offshoot.
Evolution of brain regions
· Hindbrain (”reptilian”)
· Midbrain (“mammalian”)
Fishes have midbrain too, we have hindbrains too.
● forebrain (cortex) (“human”) - most of the action happens - only 1/5 inch thick
Our bumps and grooves allow for more complex thought. i.e. rats have fairly smooth brains. We
all have the saem architecture however.
Hominid Brain Evolution - all these species have opposable thumbs, and bipedal abilities.
● Australopithecus (different genus)
● Homo habilis
● Homo erectus ● homo Neanderthalensis
● homo sapiens sapiens
Those last 3 existed within the same chronological vicinity of one another. 150k-200k years
Besides the brain, our jaw sizes are changing - since we’re cooking meat.Afew structural
Overview of Genetics
● genes build every structure in the body, including the brain and neurochemicals.
● Genes do not directly influence behavior. No big, massive behaviors are influenced.
● Abehavior (e.g. introversion, intelligence, aggression) is never the result of SINGLE
genes, but rather MULTLIPLE ones (often hundreds)
Structure of DNA:
● Human body contains 100 trillion cells
● Nucleus inside each human cell 9 except red blood cells.)
● Each nucleus contains 46 chromosomes arranged in 23 pairs.
● one chromosome of every pair is from each parent
● The chromosome are filled with tightly coiled strands of DNa
● Genes are segments of DNA(Nucleopeptides - GC & TA) that contain instructions to
make proteins - the building blocks of life
● Discrete number of categories.Any trait from any category is the result of a single gene
● Qualitative; Mendelian; not much variability
● i.e. Eye and hair color
● Dozens of (maybe a hundred of more) genes
● qualitative and on a continuum
● Great Variability
● Weight height, all psychological traits
● i.e. No single “gene” for any behavior/trait
· Indirect effect of genes on behavior. No such thing as direct!
· Genes -> Proteins -> Physiological Systems -> behavior
Beyond nature and nurture: Epigenetics
· Genetic influence is not “set in stone” at birth.
· Among other things, what we eat, drink, and do affects when, where, and how genes get
turned on or off.
· This is known as epigenetics (above or beyond genetic) – Your body changes
· Gene expression can be changed by a “second genome”, the epigene. They can come in the
forms of methyl(groups of hydrogen and oxygen) groups. Epigene is like the software, whereas
the genetics are the hardware.
● Epigenomes can be altered with tags and epigenetic therapy.
● What we eat, drink and experience can tag our genome and turn on or off genes ● The genome we are born with is flexible and open to change. (Via epigenetics)
The epigenome changes with age, which explains why two identical twins will age somewhat
differently and hwy one may get cancer or schizophrenia and the other not.
Logic of twin adoption studies
● Degree of genetic similarity (nature)
● -MZ(Monozygotic - one egg) twins - 100%
● DZ(Diazygotic - two eggs, two sperm) - 50%
● Grandparents/grandchildren, aunts, uncles, nieces, nephews - 25%
● Degree of environmental similarity (nurture) i.e.Adoptions
● Being raised together:Alot
● apart: Little
If genetics play little/no role:
● similar traits regardless of genetic relationship
● similarity increases with reared together
if Environment plays little/no role:
● similar traits regardless of similarity of environment
● Similarity increases with increase in genetic similarity.
Twin adoption studies explains genetics
Cells as building blocks
● Two types of cells in CNS
○ Glial Cells: “Glue” cells of Myelin sheath
■ facilitate neural transmission (like insulation)
■ Neurons: Nerve cells; receive, integrate, and transmit neurons
Sensory & motor (moving your body) neurons
● Efferent - away (Sensory neurons)
● Afferent - coming in (Motor neurons)
Sensory receptors in skin goes through affluent -> interneuron -> section of spinal cord ->
efferent -> bicep muscles - muscle contracts
Right motor cortex controls right side of body
Structure of Neurons
● soma - nucleus
● Axon - Myelin sheath
● Synapse - Terminal button
Overview of the action potential:
Refractory period we forget to learn more
Frontal lobes go crazy when you first start to learn. you become an expert when they stop
working a lot during activity.
Resting potential of a neuron
● inactive resting state
● More negative charge inside membrane
○ Due mostly to negatively charged proteins. (A-)
● More positive charge outside membrane
○ 10x more sodium (Na+) outside than inside membrane
● Resting state of a neuronal membrane: negative charge inside; positive charge outside
● Changes from other neurons accumulate in the neuron
● once charge become sufficiently positive (reaches threshold; depolarization), they change
the permeability of the membrane, and anA.P. occurs as an all-or-none response
Action Potential Over time
1. Resting: all channels closed
2. A.P.(Action Potential): sodium channels open (depolarization)
3. Novocane shut these sodium channels and thereby blocks action potential (numbing area)
Return to resting state: potassium channels open (repolarization)
4. Refractory period - return to resting potential
Every neuron communicates in this way:
● Synaptic Vesicles - Axom sent down, creating impact, jumpstarts action potential. Sent
down this into presynaptic neuron
○ Tiny sacs in the terminal buttons that contain neurotransmitters.
● Presynaptic neuron
● Action potential stimulates the chemicals into the terminal button.
● Postsynaptic neuron - Underneath the terminal button
● Channels receive neurotransmitters from postsynaptic neuron.
● Reuptake =