Validation was developed in an attempt to understand the emotions that a person with Alzheimer's disease or related dementia is expressing and allow caregivers to respond in a way that encourages the person to express their emotions freely.
In general, what a person is thinking on a daily basis can depend greatly on their progression in the disease process. The important thing to remember is not so much what the person is thinking, but rather to make the person feel safe, secure and stimulated.
When a person has dementia, whole experiences are constantly being lost, which makes it difficult for the brain to get its bearings. The unconscious mind fills in the gaps, swapping in an old memory or coming up with a plausible alternative.
Stress is contagious. Observing another person in a stressful situation can be enough to make our own bodies release the stress hormone cortisol. If a caregiver is anxious due to care decisions or work-related stress, they likely bring that anxiety home.