How do you weigh a soul? True enough, this was a subject of much scientific research by the middle of the last century (damn Renaissance philosophers!). Experimenters would place living things --plants, bugs, dogs, people-- on scales and wait for the moment of death. The withdrawing of a vaporous soul from its corpus was assumed to leave the body lighter, and countless theologians and reasonable scientists tried to measure the effects. Hindsight being what it is, we have only to repress a smug smirk before discussing their folly. That is, quantification of the merely qualifiable. Our thoughts, feelings, and beliefs are not to be measured like a block of marble. Our personalities, motivations, and fears can not be resigned to millimeters and degrees of angle. The measures of the mind --the weight of the soul-- are rarely so quantifiable. But even with the lack of precision inherent in the human equation, scientists can still explore the human mind.

Like all scientific research, psychologists employ the scientific method in their work (see related paper on critical thinking). A simple, five-step formula, the scientific method promotes objectivity, reduces the amount of faulty data, and marches proudly --resolutely-- from the question to the answer on empirical, repeatable observations. Thomas Aquinas is credited with the first truly usable version, and the formula has existed, mostly unaltered, for centuries. The wording of the modern version is as such: state the problem, research the problem, form a hypothesis, test the hypothesis, and finally, draw conclusions from the data. The system appears simple, but it harbors tremendous power. Conscientiously employed, it means the difference between blind guesswork and a legitimate scientific inquiry. All legitimate sciences and respectable crafts are propped up by it, not the least of which is psychology. Built on top of the scientific method are seven major techniques for psychological research. They are, in no particular order (well, okay, alphabetical order): case studies, correlational studies, experimentation, laboratory and naturalistic observation, surveys, and tests. This paper will explore each of these techniques in greater detail.

Case studies, nearly exclusive to the field of psychology, are in-depth reports on a particular individual. Researchers explore as many aspects of an individual as possible, often delving into the excruciating minutia of childhood events, daily activities, speech patterns, mannerisms, cognitive abilities and limitations, and favorite colors. Okay, not favorite colors, but just about everything else. The intention is to establish as accurate a portrayal as possible of a subject so that later researchers can look at an example of a given malady. Case studies have been conducted on autistic children, asthmatics, twins reared together and apart, and countless others. Many case studies exist on feral children, as researchers just tend to be fascinated with them. The major advantage of these reports is their stunning depth. Details are preserved on individuals whose circumstances may never be duplicated. From this, information and hypotheses can be drawn years, decades, even centuries hence. However, for all the detail of case studies, they can never include everything later researchers would want to know. What might have been an irrelevant detail for the original author might harbor an explanation for behavior or inspire a hypothesis. Too, while case studies survey an individual in detail, individuals often tell us nothing about the larger population. Safe conclusions about humans in general can really only be drawn from the comparison and contrast of many individuals. I shudder to think of the sorry state humanity would be in if I were the only representative granted to science. Depressed most of the time, lazy, a touch of anxiety panic here, a dash of social phobia there, afraid of spiders, an eye for detail, rather anal retentive, a bit obsessive compulsive, and a strong --if strange-- sense of humor. Without other individuals to balance and contextualize those qualities, the baseline for "normal" would be far askew and the explanations for human behavior would be haphazard. Only from multiple angles can an accurate picture of humanity and the peculiar quirks we suffer from be assembled.

As if to solve that problem, correlational studies are used to systematically rate and compare tens, hundreds, even thousands of individuals. They are, more precisely, statistical representations of n dimensional relationships. Correlation studies can show how strong relationships are between sets of phenomenon, such as drinking and automobile accidents, or left-handedness and capacity for evil. These studies cannot prove cause and effect, only how often one phenomenon tends to occur with another. This is easy to misinterpret, however, as a report showing that (hypothetically) people who drive Dodge Neons are statistically more likely to be pizza delivery drivers makes it intuitively much easier to assume that someone climbing into such a car does have such a job. Likewise, that statistic would not necessarily mean that something about Neons makes their drivers want to deliver pizzas, or that delivering pizzas makes people want to buy Neons, or that the numbers are not just a fluke. Correlation studies indicate statistical relationships, not that one thing causes or is caused by another. For that, other methods of investigation must be used. Nonetheless, these studies can answer important questions. They are especially useful for backing up or refuting other hypotheses, and for inspiring alternative explanations, but their limitations must be considered.

Experimentation --in the laboratory and otherwise-- grants the researcher the ability to control variables, and thus establish the cause and effect relationship missing from correlational studies. A proper experiment is, in effect, an environment where only the quality being measured is allowed to fluctuate. All other variables are controlled or eliminated, or at least that's the theory. From that, cause and effect can be established. Cause and effect are usually referred to as the independent variable and the dependent variable, in that one dimension is affected by (depends on) another (the causal variable). For an effect to be properly explained, there must be one and only one possible cause. This requires precise and rigid environments where the only sway is in the dependent variable. To make it easier to measure this, experiments are usually conducted in tandem with both an experimental group and a control group. The experimental group is subjected to the variable, while the control group is not effected by any experimental manipulation. The control group is a check on the experimental group, assuring that the results of the experiment are not environmental or caused by bias somewhere in the process. Indeed, researchers must go to ever more extreme lengths to ensure their study is devoid of unwanted manipulation; random assignment, placebos, and double-blind studies, all of which make the experiment more accurate and less subject to unintentional manipulation. Random assignment is used to ensure that neither the control group nor the experimental group is lopsided with any particular type of person, such that the results might be effected. If the entire control group was male, while the entire experimental group was female, one can see how the results might be questionable. Placebos are substances typically only used in drug studies to invalidate psychosomatic effects. They are inert pills or injections which subjects are told or suggested will affect them in specific ways. If the control group with placebos shows the same results as the experimental group with the "real" drug, one can conclude that the experimental drug is worthless and that the real money is in harnessing the power of suggestion. A double-blind study serves to keep experimenters from influencing the subjects. Humans are intelligent beasts and they pick up on subtle cues from experimenters about which group --control or experiment-- they are in. That knowledge will usually make them preform differently, perhaps to try to impress the researchers or to help them out with their study by doing what they think they want. In a double-blind study the researchers who interact with subjects are not told which group is which, and so are expected not to wink and smile and banter with impressionable subjects. Experimentation is an extremely valuable research tool. Much of science is propped up solely on its broad shoulders. However, the limitations of experimentation on humans are significant. Humans are highly subject to suggestion, and are often prey to a fantastic number of variables shaping their actions. Someone could give a dozen hypothetical reasons why they did or didn't do something, each reasonable and each compelling and each spoken while Werner Heisenberg snickers quietly to himself in the corner. If objectivity is to be assured, variables must be maintained. Where people are concerned, often that means removing as much of the human factor as possible.

Our next stop, observations (again, both inside and outside the laboratory), turn the unkempt and incorrigible "human factor" into an advantage. Where experiments propose contrived, artificial situations, naturalistic observations try to study humans without any pretenses. In the wild, as it were. Akin to the participant observation of anthropology and sociology, psychologists merely watch people do their humanly thing. Unlike experimentation, observations cannot establish cause and effect. They describe a behavior, rather than explain it. Much like the statistics of correlational studies, observations merely show what is occurring (assuming the method is sound) without commenting on why. However, naturalistic observation --that is, going out to a location and just watching-- has a significant advantage which must not be understated: it is cheap. Laboratory observation incurs the cost of infrastructure, plus any machinery or measuring devices required, but its twin brother may require nothing but a note pad and a pen (easily pilfered from a nearby classroom). Laboratory observation may involve diodes and sensors and heavy, menacing-looking contraptions all in a controlled environment. Experiments and other methods can quickly become fabulously expensive. Naturalistic observation can mean nothing more than a trip to the park to see how people act around strangers. Researchers must be careful not to interfere with or influence their subjects, and to try to stay as unobtrusive as possible. This is crucial, as people are just as easy to influence in their natural habitats as in the artificial environments of an experiment (Heisenberg allows a burst of laughter to escape his smirking lips). Likewise, one can not know, then, what is being measured; normal human reactions or normal human reactions to the researcher. But both methods' inability to explain phenomenon limits their use. Often they are used as preliminary studies, as it is easier to investigate a behavior already described.

The bastard brother of correlational studies, the survey, are a helpful --if dangerous-- research tool. They can provide important and useful data about large populations, but their limitations are numerous. The one advantage they have is that they directly illicit responses from large groups. Rather than determining political opinions or common life experiences through some round-about method, researchers simply ask the population. It can be very straight-forward. Surveys are usually used to compile data about a group's attitudes, opinions and experiences. A researcher might wonder how many residents of Canton Township tip their pizza delivery drivers (hint: not enough), or if dyeing your hair blond makes women flock to you (not really). Instead of constructing and conducting an elaborate experiment, one could just ask people what they do or what they think. However, a significant problem is obtaining a representative sample --a small group that reflects the larger population. It would be impractical to ask everyone in the country what their favorite kind of donut is, so researchers survey small, manageable groups and extrapolate the results to the larger population. But valid representative samples are difficult to obtain. Similarly, the results of even a proper representative sample can be subject to much error. People have a tendency to present themselves in a more positive light than they really are, exaggerating their virtues and concealing their sins. No one wants to admit to a researcher that they think or do something which society looks down on. Likewise, people can be easily swayed by the very wording of a question. Researchers must be sure to phrase their questions in a neutral way so people are not turned off by negative words.

Tests can provide statistical information and predictions on the personality traits, emotional states, aptitudes, interests, abilities and values of an individual. They are useful in many fields for evaluating or ranking individuals in simple, quantitative categories. Testing is simple, cheap, and can be very accurate. Unfortunately, like surveys, the way a test is structured and written can drastically affect how people react to it. Questions written at or above college level vocabulary may inadvertently test for reading ability rather than what the test was intended for. Test creation poses many problems. To be scientifically useful, a test must be standardized and reliable. That is, a test must have clear rules for taking and scoring, and give consistent results for like populations.

Across all types of psychological testing --but experimentation perhaps most especially-- ethics must be considered. Whether studying humans or animals, researchers must balance the value of the study against the rights of the subjects. With humans, the dignity and welfare of the subject must be considered, with particular consideration for their physical and mental wellbeing. They must be advised of any danger inherent in the study, unless deception is necessary. In such a case, researchers must prove that deception is crucial to obtaining a natural reaction, and thoroughly debrief the subject afterwards about the risks and purpose of the study. Ethical requirements for animal studies are much lower, although psychological research tends to not use very many animal subjects. Nonetheless, studies on animals can teach us things which would never be possible with humans. The debate continues, however, but the treatment of animal subjects has been improving as federal guidelines become more strict.

Yet another tasty morsel from Noding things you've written before.
Origionaly from a lame psychology course in "college."