1. How do we know that the increased dreaming shown by Dement's research participants was due to REM deprivation specifically and not due to being awakened repeatedly?

Dement was unable to account for this possibility because he had no good way to tell when his research participants were in REM sleep.

Dement included a control condition in which participants were awakened repeatedly during non-REM periods of sleep, as a comparison.

Dement used "light sleepers" as his research participants, and these people were prone to waking up repeatedly throughout the night anyway.

Dement failed to make the important distinction between REM sleep and non-REM sleep, and this is a major criticism of his research.

2. Sperry and Gazzaniga concluded from their research on split-brain patients that

split-brain surgery is a radical but effective cure for certain serious mental illnesses, such as schizophrenia

each hemisphere of the brain has specialized functions and is really a mind of its own

the hemispheres of the brain cannot operate independently and must be connected in order for a person to function.

splitting the hemispheres of the brain produces radically different personalities that alternate.