Diminished Capacity in Psychology: Definition & Examples

Instructor: Michael Quist

Michael has taught college-level mathematics and sociology; high school math, history, science, and speech/drama; and has a doctorate in education.

When you have diminished psychological capacity, you no longer have the ability to make effective, reasonable decisions regarding your life. In this lesson, we'll discuss the definition of diminished capacity and look at some examples.

What is Diminished Capacity in Psychology?

You're at home alone. You don't know what's wrong with you, but you don't feel well and you're struggling to get up off the floor. Grabbing your phone, you manage to call 911. The EMTs notice that you've not been eating well, you're confused, you haven't bathed in many days, and there's no evidence that you have recently eaten. Something is definitely wrong with you.

Diminished capacity is a condition where you are no longer capable of making effective decisions about your life. It is also called a loss or lack of 'competency'. Capacity can refer to your ability to decide things (decisional capacity) or your ability to take effective action (executional capacity).

Why Does it Happen?

Diminished capacity occurs as a result of damage to the brain. For example, dementia (a decline in your memory or thinking skills) can produce a condition where you no longer remember how you're supposed to behave. Psychological conditions, such as schizophrenia (fragmented thought processes combined with delusions and illusions), can create a situation where you're no longer perceiving reality effectively. Psychopathy is a state where you have a limited ability to experience emotions and may not understand the consequences or moral implications of your decisions and actions. Damage to emotional processing centers, such as due to a physical blow to the head, can cause you to be unable to control your emotions. In each of these cases you may be considered to have diminished capacity, which generally means that society will not allow you to remain completely independent.

Movie Madness

You are fascinated by a certain movie, to the point of obsession. You watch it over and over again and imagine yourself as the protagonist. As you spend your time constantly within this limited environment, you find that aspects of your life outside the movie become more difficult to understand and deal with. You don't understand the need to pay your bills or even go to work. After all, you are now a different person! As the delusion persists, you begin to believe that you need to follow the path of the protagonist, which includes the murder of an interfering neighbor. Finally, you take action.

During your trial, medical professionals come forward to present physical evidence. Your brain has been altered by your obsession! Certain pathways have been rendered useless, while others have become overdeveloped and prominent. The argument is raised that you no longer have the ability to correctly evaluate your actions. Until you are treated, you are considered to have diminished capacity.

Alzheimer's Disease

You can't remember the things the way you used to. You don't know the people at the door who claim to be your family. You forget that you left the burner on in the kitchen. The people on the television don't seem to make any sense any more. You have Alzheimer's Disease.

As your brain begins to break down, tiny changes cause loss of blood supply to parts of your cerebral cortex (the wrinkled, blanket-like surface of your brain where your awareness resides). You begin to lose regions that hold memories, while others begin to cross-connect, causing the information to become confused. As the losses build up, your ability to manage your life decreases. You are now in a state of diminished capacity.

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