The Science of Psychology 39empirically should be examined using established scientific approaches. One shouldn’t
accept anything at face value but should always ask, “How do you know that? What is
the evidence? Can you be more specific in your terms?” (These are more examples of
those important questions to ask when thinking critically.) For example, many people
still believe that astrology, the study of the supposed influence of the stars and planets
on the birth of an infant, can be used to make predictions about that infant’s person-
ality and life events as he or she grows. But scientific investigations have shown us,
time after time, that astrology is without any basis in truth or scientific fact (Dean &
Kelly, 2000; Hines, 2003; Kelly, 1980; Wiseman, 2007).- All evidence is not equal in quality. One of the most important, often overlooked
steps in critical thinking is evaluating how evidence is gathered before deciding that
it provides good support for some idea. For example, there are poorly done experi-
ments, incorrect assumptions based on correlations rather than experiments, studies
that could not be replicated, and studies in which there was either no control group
or no attempt made to control for placebo effects or experimenter effects. There are
also studies that have been deliberately manipulated to produce the findings that the
researcher (or whoever is paying the researcher) would prefer. For example, the results
of a study on the effectiveness of a particular drug would be immediately suspect if
the researcher is being paid by the company making the drug. As a critical thinker,
you should be aware that the more wild the claim, the better the evidence should be:
For example, I have not yet seen any evidence that convinces me of alien visitations or
abductions! - Just because someone is considered to be an authority or to have a lot of
expertise does not make everything that person claims automatically true.
One should always ask to see the evidence rather than just take some expert’s word
for anything. How good is the evidence? Are there other alternative explanations?
Is the alternative explanation simpler? If there are two explanations for some phe-
nomenon and both account for the phenomenon equally well, the simplest expla-
nation is more often the best one—a rule of thumb known as the law of parsimony.
For example, let’s look at crop circles, those geometric patterns of flattened crop
stalks that have at times been discovered in farmers’ fields. Two possible explana-
tions for crop circles exist: Either they are made by aliens in spaceships—as is the
Many people believe that crop circles are created by alien visitors, despite clear evidence that crop
circles are hoaxes created by ordinary people.