MCAT Diaries: Psychology Day 1

Studying for the MCAT can be a terrifying experience if one looms over the reading material and hours of practice, but with efficient reading and studying, the preparation can be less scary. I will be summarizing the material from my Blueprint books to prepare for my test. Join me for the journey!

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Much of modern medicine heavily relies on the research of doctors and teams of techs and participants. All of research has led to multiple discoveries in various areas of science, and each of these has independent, or X, and dependent, or Y, variables.

·        X is a manipulated variable that is expected to change Y in some way. X is the vertical axis on a graph.

·        As stated, prior, Y is expected to change with the manipulation of the X variable. If the effect of Y increases or decreases from the manipulation of X, then a cause-and-effect relationship can be inferred.

Once you can display a relationship between X and Y, one must be able to apply a method of study to analyze it further. The types of studies that these teams of researchers conduct can include experimental or observational methods:

·        Experimental: Trends of this study include manipulation of the X variable and a record of one timepoint.

o   Non-blinded, Single-blinded, Double-blinded

§  Non-blinded: everyone knows

§  Single: either the participants or the researchers of the study know which randomly selected group/cohort each participant is in but not both

§  Double: neither the participants or the researchers know which group/cohort the participants have randomly been assigned to

o   Randomized Controlled Trial (RCT)

§  Randomized: Patients/Participants are randomly selected to the tested treatment (examples: medication, therapy, etc.), a negative control (examples: placebo or sugar pill), or a positive control (examples: a medication with the desired and known effect to be used as a comparison).

·        Observational: There is no manipulation of the X variable; rather, the relationships held between the variables are observed.

o   Cross-sectional/Correlational Study: At a single point in time, participants representative of a population are observed for various characteristics/diagnoses to observe correlations.

§  Longitudinal study: Rather than looking at results presented at a single time, a longitudinal study observes the effects over a period of time.

·        Cohort: The participants are split into categories, such as age or race, and certain characteristics are studied from there.

o   Prospective: looking into the future

o   Retrospective: looking into the past

o   Case-control Study: This study method compares individuals with a sought out diagnosis or prognosis to those who have not been diagnosed with that illness. This observes the differences between the selected individuals or populations.

§  Importance lies in epidemiology.
Best to worst: RCT, Cohort, Case-control, Case study

Although the variables may seem cut and dry, more than 1 X and/or Y variable can be determined. For example, a confounding variable may mislead researchers from determining the true cause of Y. Then, a mediating variable may be induced from the current situation, or variable X, and these choices/events increase the outcome of Y. Lastly, a moderating variable will alter the intensity of Y.

Now, that the basics of a research study are known, the following qualities aim to conduct an objective and fair study:

·        Value
·        Validity
·        Relevant choice of participants/Valid representation of a population
·        Favorable risk-benefit ratio
·        Independent review to review bias, conflicts of interest, or ethical concerns
·        Consent from the participants

A fairly common study is nature versus nurture, which is to determine what phenotypical results are derived from environmental and genotypical effects.

·        Twin studies: Identical (monozygotic) and Fraternal (dizygotic)

·        Most phenotypes have a heritability of 0.3-0.6, and schizophrenia has a heritability of 0.8.

Some considerations while conducting your study include the validity (accuracy) or the reliability (preciseness) of your results. Whether you are studying the number of pounds of food that your dog consumes in 5 minutes or aiming for a new and improved seizure medication, the results of the study must be valid enough to display a clear trend between the X and Y variables. The accuracy of the data is especially important. For example, in determining the effect of a certain treatment for thyroid hormone (TH) management, a measured dosage of levothyroxine was given and raised the patient’s thyroid hormone Z ± 0.1 mg/mL of blood, where Z is the increase of the hormone and 0.1 is the confidence interval in the report. If the results of the medication are measured incorrectly, this can lead to inaccurate results. Some considerations with validity include:

·        External: how the method is applied to a “normal” or general setting

·        Internal: the conclusions of the study; did the manipulation of X indefinitely affect the intensity of Y

·        Content: the extent of measurements

·        Construct: how well the method was to the study’s intended goal

·        Criterion: prediction of the performance of an outcome

The reliability of the results matters as well. If you have spotty conclusions or measurements, then the true effect of the manipulated X variable is unknown.

Although the independent review described earlier aims to eliminate as much bias as possible, possible methods, such as opinion polls or questionnaires (from the Likert scale), may contain acquiescence, or an immediate response of “yes” from an unknowledgeable participant, and self-reported bias, or the want to fit into social values.