Body-as-Subject in the Four-Hand Illusion

Area of Science:

• Neuroscience
• Philosophy of Mind
• Human-Computer Interaction

Background:

• Phenomenological theories suggest individuals experience their body parts exclusively as either subject or object, not simultaneously.
• The Experiential Exclusion Thesis posits a mutual exclusivity between experiencing a body part as subject versus as object.

Purpose of the Study:

• To investigate the philosophical implications of the novel
• four-hand illusion
• on the body-as-subject/body-as-object dichotomy.

Main Methods:

• Participants used a head-mounted display (HMD) to adopt an experimenter's first-person perspective (1PP).
• Participants observed four hands: the experimenter's (1PP) and their own (third-person perspective, 3PP).
• Synchronous visual and tactile stimulation of index fingers induced the illusion, leading to a sense of owning additional hands.

Main Results:

• The study induced the
• four-hand illusion
• , where participants felt ownership of virtual hands.
• The subjective experience of the first-person perspective (1PP) hands, involving kinesthetic and visual senses of movement, served as a counter-example to the Experiential Exclusion Thesis.

Conclusions:

• The findings challenge the strict mutual exclusivity between experiencing a body part as subject and as object.
• It is possible for healthy individuals to simultaneously experience the same body part as both subject and object.
• The distinction between body-as-object and body-as-subject is not as rigid as proposed by phenomenological theories.