In 2013, an estimated million adults in the united states had alzheimer disease.

In 2013, an estimated 5.7 million adults in the United States had alzheimer disease.

Explanation:

Alzheimer's disease is the most common cause of dementia and causes destruction of gray brain tissue and atrophy of the brain. The disease also damages the chemical systems of the brain. Alzheimer's disease, like most other dementing diseases, occurs primarily in the elderly.

The disease was named after the German psychiatrist Alois Alzheimer, who first described the disease in 1906.   Alzheimer's disease destroys a person's memory and eventually other mental abilities, as well as physical and speech abilities.

i believe the answer is:   psychological  experiment

in this experiment, wilhelm wundt became the first person that implement scientific method in analyzing the pyschological phenomenon.

due to this result, wilhelm wundt also able to make psychology to be acknowledged as a separate scientific field from biology.