Final answer:
The most likely altered state of consciousness in this scenario is hypnosis, which involves extreme self-focus and attention and minimal attention to external stimuli.
Step-by-step explanation:
The most likely altered state of consciousness described in this scenario is hypnosis. Hypnosis is a state of extreme self-focus and attention in which minimal attention is given to external stimuli. In the scenario, the specialist puts Jonathan into a relaxed state by repeating a simple phrase over and over again, guiding him to focus on the specialist's words and be open to the process of hypnosis.