Bad Psychology

Psychology is the science of human thought, emotion, and learning, including interpersonal relationships. Bad psychology is what happens when a fanbrat attempts to use psychological concepts in fan fiction... and fails. Badly.

It is common in bad hurt/comfort fics, in stories involving rape, incest, abuse, and angst. It almost always involves pulling the canons OOC, because bad psychology inevitably involves unrealistic human behavior.

Bad biology is a similar offense.

Unrealistic Relationships
Unrealistic depictions of love and human relationships. Overlaps with OOC and bad slash.
 * Stockholm syndrome, badly done: Depicting someone falling in love with a captor or abuser as a perfectly rational and beautiful thing, rather than a combination of brainwashing and determination to survive.
 * Any of the myriad incest fics in which somehow, incest is present without a seriously messed-up family life (or at least a childhood spent apart).
 * Depicting an abusive relationship, or one involving stalking, as perfectly healthy.
 * Having True Love make a relationship automatically perfect. (I.e., the idea that people who are in love will never fight, never annoy each other, and never disagree.)

Misused Mental Illness

 * Magically curing mental illness just because the character who had one fell in love. Actually, magically curing mental illness, period.
 * Asperger's Syndrome CANNOT be cured by having a foursome.
 * Melodramatic depictions of self-injury, which use self injury mostly to accent how sad someone is (usually about how their Twu Wuv has rejected them), without actually researching what self-injury is and why people use it as a coping strategy. Even worse: Using it as a symbol that a character is "emo."
 * Causing characters who have a mental illness to become randomly and severely violent, even though it is completely out of character for the person in question.
 * Giving a character a mental illness and failing to do even the most basic research. Schizophrenia and multiple personality disorder? NOT the same thing.
 * Using mental illness as a way to bash a character.
 * Using mental illness as a joke.
 * Using conditions like ADHD or dyslexia as excuses for horrible writing (instead of as reasons to find a beta).

Badly Depicted Trauma/Angst

 * Most examples of wangst.
 * Depicting a particularly resilient character as ridiculously traumatized by a minor event that, given his personality, shouldn't faze him much.
 * Conversely, having characters react nonchalantly to something that should by rights give them serious PTSD.
 * Healing sex: A character traumatized by rape suddenly being cured of their trauma... because someone else has sex with them.
 * Trivialisation, especially trivialised rape.
 * Randomly having characters commit suicide when they wouldn't logically do so. (Let's see... Character X, a resilient, mentally stable sort of fellow, has lived through the end of the world, lost his family, and gotten through the grief with his sanity mostly in one piece. After making a new life for himself as part of a close-knit ragtag crew of survivors, he meets Mary Sue, falls in love with her after two minutes, and sees her die after two days. He promptly commits suicide because he can't live without her. Uhh....)

Being Clueless About Psychology In General

 * Giving a character a ridiculously high or low IQ score. If your fanfic writer quotes an IQ score over 200 for a character, assume they don't know squat about IQ tests. Even if it's just over 150, assume Mary Sue.
 * Having therapy or medication be a magical cure for mental illness&mdash;or else a sign of weakness. (OK if a character has these opinions; not OK if the story assumes that this is actually true in a Real World-like continuum.)
 * Having characters who usually think logically react emotionally to something that isn't out of the ordinary for them (or vice versa).
 * Unrealistically mature or immature behavior from children and teens. Ignoring the basic principles of child development isn't a good way to write child characters. "He's gifted" isn't an excuse to make a child act like an adult. Similarly, if your fourteen-year-old Mary Sue acts like a battle-hardened veteran (without, in fact, being a battle-hardened veteran), you need a year at an OFU&mdash;stat!
 * Having a character act in a way he is not accustomed to acting, without giving justification for why he is acting that way. People do things for a reason. (See also: OOC.)

However, beware:
Some continua do not have the same rules for psychology as World One. If the world in question depicts psychology, mental illness, or human behavior in unrealistic ways, the fan author cannot be blamed for it. FicPsych cautions agents not to bring residents of these continua into a Reality Room, as this may result in a re-writing of the character's psyche.

It's also important to take into account non-human psychology. Arda Elves who are raped will fade, for example; a different response from a human's. Orcs in some canons (there are multiple orc variations) are incapable of kindness. Vulcans have different minds and personality tendencies from humans, as do Klingons, Romulans, Ferengi, and many other Star Trek species. House-elves truly do love being servants (but still don't like being mistreated). Dracula-verse vampires cannot be reformed by Twu Wuv. The minds of digital or robotic characters, energy creatures, and Cosmic Horrors can be so alien as to be difficult or impossible to understand. So, bad psychology can sometimes mean applying Real World psychology to species which are not from the Real World&mdash;something as silly as trying to apply your knowledge of raising kittens to the process of growing tomatoes!

Additionally, mentalities and even mental capabilities may change with time period or setting. Historical settings may feature a shorter lifespan and thus shorter childhoods and adolescence, and thus younger individuals would be seen behaving as 'grown-ups.' The demands of a setting affect the characters that live there: in a setting where most people are illiterate, not being able to read is not a sign of stupidity. A culture with a severely different viewpoint than a basic modern one may seem to make alien decisions to the reader. In settings where one is expected to learn a trade, a tradesman might be able to perform specific tasks at a high-functioning level (say, ship navigation, which requires math and measurement) while performing other tasks at a much lower level. Setting counts as much as species when it comes to what can be considered 'normal' psychology for any given individual in a story.