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Psychology and DNA: Probability, Not Certainty

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I recently finished Sam Kean’s (2012),  The Violinist’s Thumb the history, the present, and the future of DNA research. Kean writes, “Genes don’t deal in certainties; they deal in probabilities.” I love that – and I’m using it the first day of Intro Psych next term: “Psychology doesn’t deal in certainties; it deals in probabilities.”

I already talk about correlations as probabilities. The stronger the correlation, the higher the probability that if you know one variable, you can predict the other variable.

In the learning chapter, it’s not unusual for a student to say, “I was spanked, and I turned out okay.” Now I can repeat, “psychology doesn’t deal in certainties; it deals in probabilities.” When children are spanked, it increases the probability of future behavioral problems (Gershoff, Sattler, & Ansari, 2017). It is not a certainty.

Whenever aggression comes up as a topic, a student will say, “I play first-person-shooter games, and I’ve never killed anybody.” Again, “psychology doesn’t deal in certainties; it deals in probabilities.” Playing violent video games increases the chances of being aggressive. Watching violent movies increases the chances of being aggressive. Listening to violent-themed music increases the chances of being aggressive. (List is not exhaustive.) The more of those factors that are present, the greater the probability of behaving aggressively (Anderson, C, Berkowitz, L, Donnerstein, E, Huesmann, L, Johnson, J, Linz, D, Malamuth, N, & Wartella, 2003). It is not a certainty.

A student says, “I was deprived of oxygen when I was being born, and I haven’t developed schizophrenia” (McNeil, Cantor-Graae, & Ismail, 2000). (Okay, I have never had a student say this, but I wanted one more example.) Being deprived of oxygen at birth increases the probability of developing schizophrenia. It is not a certainty.

Any time a student reports an experience that does not match what most in a research study experienced, I can say “Like genetics, psychology doesn’t deal in certainties; it deals in probabilities.”

 

References

Anderson, C, Berkowitz, L, Donnerstein, E, Huesmann, L, Johnson, J, Linz, D, Malamuth, N, & Wartella, E. (2003). The influence of media violence on youth: . Psychological Science In The Public Interest (Wiley-Blackwell), 4(3), 81–110. https://doi.org/10.1111/j.1529-1006.2003.pspi_1433.x

Gershoff, E. T., Sattler, K. M. P., & Ansari, A. (2017). Strengthening Causal Estimates for Links Between Spanking and Children’s Externalizing Behavior Problems. Psychological Science, 95679761772981. https://doi.org/10.1177/0956797617729816

Kean, S. (2012). The Violinist’s Thumb. New York City: Little, Brown, and Company.

McNeil, T. F., Cantor-Graae, E., & Ismail, B. (2000). Obstetric complications and congenital malformation in schizophrenia. In Brain Research Reviews (Vol. 31, pp. 166–178). https://doi.org/10.1016/S0165-0173(99)00034-X

About the Author
At Highline College near Seattle, Sue Frantz is working on her third decade in the psychology college classroom. Throughout her career, she has been an early adopter of new technologies in which she saw pedagogical potential. In 2009, she founded her blog, Technology for Academics. The blog features both new tech tools and tips for using not-so-new tools effectively. She currently serves as Vice President for Resources for APA Division 2: Society for the Teaching of Psychology. In 2013, she was the inaugural recipient of the APA award for Excellence in the Scholarship of Teaching and Learning at a Two-Year College or Campus. In 2016, she received the Charles L. Brewer Distinguished Teaching of Psychology Award. As the newest contributor to the Instructor Resource Manual for the David Myers and Nathan DeWall Introduction to Psychology textbooks, she is excited to bring teaching resources to you in this venue.