Final answer:
Hypnosis involves a state of altered consciousness, held by the dissociation theory, which Ernest Hilgard's research supports. This theory proposes that hypnosis causes a split in consciousness between planning and monitoring functions.
Step-by-step explanation:
The theory that proposes that hypnosis induces a split between two aspects of the control of consciousness, namely the planning function and the monitoring function, is known as the dissociation theory. This view suggests that hypnosis creates a dissociated state of consciousness. For instance, while driving to work, one might operate the vehicle without conscious awareness, focusing attention elsewhere. Similarly, during hypnosis, one part of consciousness is responsive to suggestion while another part may retain awareness of reality, as shown in experiments where subjects indicated feeling no pain in an ice water test but still pressed a button to indicate otherwise. This divergence indicates different levels of consciousness operating simultaneously.
Ernest Hilgard's research is a significant support for the dissociation theory, showing that hypnotized individuals can experience a split in consciousness where one stream responds to the hypnotist's suggestions while another stream remains aware of reality. The theory stands in contrast to the social-cognitive theory, which states that hypnotic behavior is a performance of the expected social role rather than a change in the state of consciousness.