Human behavior studies have much to offer nonfiction writers. In my teaching, I work to aid fellow authors to write about themselves and others by presenting a believable picture of character. Together, we study human behavior to draw insights from such fields as psychology, psychiatry, education, sociology, and social work.
Dust off textbooks. Seek librarian recommendations. Search the Internet or use other popular sources at your disposal. These will lend accuracy and authenticity to your writing, in building character, specifying age, describing symptoms, observing dynamics, creating tension, and more. Why not use the art and science that has studied human behaviors? It may help resolve simple or complex decisions for the story teller.
Do you want to introduce the age of a four-year-old in a different way? Look at child development texts.
“How old are you?”
Johnny looked up to his grandmother, “Why?”
When she smiled, he raised four fingers and reported loudly, “four!” 
Perhaps a character in your story is addicted to a substance and is in recovery. There is a vast literature from which to draw.
The counselor was sympathetic but stern: “Stop using? That is only half the battle. You really need to create a new life, so that everything that brought you to your addiction does not catch up with you again.” 
How about a character in a psychotic state? Abnormal Psychology provides a description of relevant symptoms, treatment and more. For example, Delusions are fixed beliefs an individual holds even when reality contradicts them.
John spoke with authority, “Jesus told me. I speak in His name.” Then in anger he added, “I have to leave for home.”
“Have you spit out your Thorazine again?” responded the nurse. 
Here are a few summary points — manuscript and author benefits — of using human behavior studies in your writing.
- A thorough understanding of what is being portrayed, informed by the historical or current knowledge of human behavior studies is crucial to good writing. It promotes clarity and detailed progression on the evolution of a character and the development of a scene.
- Empathy for the human condition stems from a better understanding of the dynamics of a situation. Descriptions that show the author’s awareness, and Emotional I.Q. contribute to subtlety in writing and potentially greater insight for the reader.
- A better understanding and empathy for a character may lead to epiphanies and insights that enrich the page. When captured, such epiphanies offer resolution and relief to the reader. That I consider an author’s psychological debt can be gracefully delivered.
- At times, reliving a traumatic moment might trigger the author’s defenses. Self-examination deepens the layering in a story when we persist and examine what may be the underlying reaction.
- In creative non-fiction, we can count on the author to address personal trauma as they build the story arc. In uncovering stressful memories some of the ways we as authors defend ourselves include forgetting, suppressing the detail, experiencing block, and even denial or inaccurate portrayal of the emotional truth. To spark what may need more interior search, description, insight, short of seeking therapy, may be adequately met via the study of human behavior. Readings can provide insights and provoke the author to better express what the page requires.
- When family challenges the memoirist for his/her perceptions and point of view, the author may feel better prepared to make their case having built up the backup by credible literature.
It’s all about taking advantage of systematic observation and the latest information available, a necessary tool for the thoughtful painter of stories.
 For general reading, consult the following: Shaffer, David R., and Katherine Kipp. Developmental Psychology: Childhood and Adolescence, 9th Ed. Belmont, CA: Wadsworth [Cengage Learning Series], 2013.
 Information on child development by age [from The Center for Parenting Education] can be found here: http://centerforparentingeducation.org/library-of-articles/child-development/child-development-by-age/#four
 For general information, see: Galanter, M.D. ed., Marc and Herbert D. Kleber, M.D. ed.; Kathleen T. Brady, M.D. Ph. D. ed.. Textbook Of Substance Abuse Treatment, 5th Ed. The American Psychiatric Publishing, 2015.
 For information on this specific example, see: Bestor, Sheri Mabry. Substance Abuse: The Ultimate Teen Guide. Lanham, Maryland: The Scarecrow Press, Inc., 2013. Print. 76-81.
 For general information, see: Oltmanns, Thomas F., and Robert E. Emery. Abnormal Psychology. Upper Saddle River, N.J.: Prentice Hal, 2012.
 For information on this specific example, see: Xavier, Amador, Ph. D. I Am Not Sick. I Don’t Need Help! How to Help Someone with Mental Illness Accept Treatment. Peconic, New York: Vida Press, 2012. Print. 185-186.
Sophia Kouidou-Giles was born in Thessaloniki, Greece, and resides in Seattle, WA. With a BA in psychology and an MSW in social work, she worked in child welfare for 34 years, publishing articles in professional Journals. “Transitions and Passages,” a poetry chapbook was awarded recognition in a juried competition. “Life on Egypt Street” a short story, is included in the Time Anthology; “Walking on Rhodes,” a poem, is published in Voices magazine. Member of AWP and PNWA, she is currently working on poetry and a memoir. Follow Sophia @kouidou and visit her on Facebook.