Final answer:
Prosopagnosia, or face blindness, is a psychological disorder that can be observed when a person fails to adequately recognize faces, impacting social functioning. Schizophrenia and major depression are also examples where daily functioning can be severely affected due to symptoms like disordered thoughts and sadness.
Step-by-step explanation:
An example of a psychological disorder that can be observed based on failure to function adequately is prosopagnosia, also known as face blindness. This condition prevents individuals from recognizing faces which is an essential social function. Those with prosopagnosia might not recognize the faces of celebrities, historical figures, family members, or even their own reflection in the mirror, which significantly impacts their ability to interact and function socially.
Other psychological disorders, such as schizophrenia and major depression, can also lead to a failure to function adequately. These illnesses can severely interfere with a person's ability to carry out everyday activities due to symptoms like disordered thoughts in schizophrenia or overwhelming sadness in major depression. These disorders illustrate how mental illnesses can profoundly affect an individual's daily functioning and quality of life.