Brain & Behavior: Research Methods and the Tools Behind the Science
Learning Objectives Understand the difference between opinions, hypotheses, and theories What constitutes “proof” and why scientists “hedge” so much Experiment vs. correlational studies: the strengths & weaknesses Learn about the technology we have for seeing parts of the brain How we study brain activity & correlate this with behavior Learn how we study the effects of heredity on behavior Learn about the ethical use of humans & animals in research
Opinions, hypotheses, and theories Opinion: a personal belief or judgment that is not founded on proof or certainty (wordnet.princeton.edu/perl/webwn) Hypothesis: a statement about the expected relationship b/w two (or a handful more ) variables – good hypothesis is supported with solid rationale based on empirical evidence Theory: an attempt to explain the interrelationships between numerous variables which relate to a common phenomenon & help us to understand the phenomenon
Scientific “proof”: why scientists “hedge” so much Scientists rarely study whole populations. They study “samples”. They uncover some “truth” in their sample, then estimate the probability that this “truth” would surface in the population. All they know is the probability that something would be found in the population Significant results or effects are those which would probably be found in the population p < .05 … the probability that we’re wrong, that there’s actually no effect in the population, is less than 5%
Acceptable Hedge Words The results suggest… The results are consistent with… One possible interpretation… These results imply… NEVER say “these results prove… unless???
Experiments Manipulate one or a few INDEPENDENT variables to see what effect they have on one or more DEPENDENT variables. In the meantime, they eliminate or control all other EXTRANEOUS variables, so that they do not become CONFOUNDS To “manipulate” an IV means to test at least two categories (levels) of the variable Used to establish cause & effect
Correlational studies Variables are measured and recorded, but NOT manipulated A correlation coefficient (r value) is calculated – this tells us how strong or weak the relationship is, as well as the direction of the relationship The SIZE of the r value = strength -1 ……….. 0 ……….. +1 perfect no rel perfect The SIGN of the r value = direction positive = as scores increase for one variable, they increase for the other (and vs. versa) negative = as scores increase for one variable, they decrease for the other
Advantage Disadvantage Help establish cause & effect So much control makes them artificial limiting their generalizability Experiments Correlational Studies Less artificial, Good for making predictions Cannot establish Cause & effect Regardless, replication & converging lines of evidence are necessary to establish a finding’s validity
Staining & Imaging Neurons Golgi stain Myelin stain Nissl stain green-fluorescent Nissl stain Black images are neurons Myelin is stained blue
Other neuronal imaging techniques Autoradiography: allows us to see neurons, and identify which neurons are active Must inject a radioactively labeled substance like 2DG Computer color-coded autoradiograph of neuronal nicotinic receptors in a sagittal section of rat brain. Autoradiograph of blood flow in the brain
Immunocytochemistry: attach a dye to antibodies , inject the antibodies into the organism, remove the tissue and observe Rat cortical stem cell differentiation: monitored using multicolor immunocytochemistry
In situ hybridization: complementary strands of DNA are created and made radioactive… these then bind with mRNA inside the cell… pinpoints gene activity
Brain Imaging Techniques for Humans & Animals Computed tomography (CT) scans Why would a conventional x-ray of the brain not work? CT uses a computer to combine many 2D x-ray scans at different angles to form a 3D image of the brain Allows us to see structure But not function One of the best ways of detecting tunors
Magnetic Resonance Imaging (MRI) measures radio-frequency waves emitted by different elements when subjected to a magnetic field allows greater imaging detail but very expensive and still cannot see function CT scan MRI
Functional MRI (fMRI) Superimposes activity over structure What advantage does this confer over MRI as far as brain behaviorists are concerned?
Positron Emission Tomography (PET) inject a radioactive labeled substance more active neurons take up more of the substance – can see activity but not precise location
Manipulating the Brain Positions instruments in 3D space Vernier scale
Investigating the effects of heredity Correlational studies: compares concordance rates family study: family members vs. relatives adoption study: biological parents vs. adoptive parents twin studies: MZ vs. DZ twins Garrett maintains that twin studies eliminate confounds due to environment, but… MZ are exposed to more similar environments than DZ… where and when???
Two cardinal sins: Fabrication & Plagiarism Fabrication: making data up or altering the data collected Plagiarism: intellectual theft of ideas, data, or data interpretation No need to cite if… stating general knowledge reporting/interpreting your own research results describing your idea – an idea not already published Why is fabrication considered worse??
Research using Human Participants Reviewed by IRBs to ensure compliance with federal code Cannot be more than minimal riskunless get signed informed consent Signed consent is also required for vulnerable populations Deception Justified, no other alternative, not deceiving on anything participants would want to know before deciding to participate, and deception cannot be greater than minimal risk Participant safety & well-being is paramount!!!
Research using Animal Subjects Reviewed by IACUC’s to ensure compliance with the Animal Welfare Act Typically , approval for animal research is more difficult than for human research… why? Justification must increase proportional to pain & distress Must be adequately trained Use the lowest level of noxious stimuli possible Try it on self first Careful attention to health and husbandry issues