Integrated information theory

Integrated information theory (IIT) attempts to explain what consciousness is and why it might be associated with certain physical systems. Given any such system, the theory predicts whether that system is conscious, to what degree it is conscious, and what particular experience it is having (see Central identity). According to IIT, a system's consciousness is determined by its causal properties and is therefore an intrinsic, fundamental property of any physical system.Note that Z t − 1 { extstyle Z_{t-1}} may be different from Z t + 1 { extstyle Z_{t+1}} , since the elements that a mechanism affects may be different from the elements that affect it. P t ± 1 { extstyle P_{tpm 1}} denotes a pair of partitions, one of which is considered when looking at a mechanism's causes, and the other of which is considered when looking at its effects.The irreducibility of the cause repertoire with respect to P t − 1 { extstyle P_{t-1}} is given by φ cause ( m t , Z t − 1 , P t − 1 ) = EMD ( p cause ( z t − 1 | m t ) , p cause ( z 1 , t − 1 | m 1 , t ) × p cause ( z 2 , t − 1 | m 2 , t ) ) { extstyle varphi _{ extrm {cause}}(m_{t},,Z_{t-1},,P_{t-1})={ extrm {EMD}}(p_{ extrm {cause}}(z_{t-1}|m_{t}),,p_{ extrm {cause}}(z_{1,t-1}|m_{1,t}) imes p_{ extrm {cause}}(z_{2,t-1}|m_{2,t}))} , and similarly for the effect repertoire.Note that the minimum-information 'partition', despite its name, is really a pair of partitions. We call these partitions MIP cause { extstyle { extrm {MIP}}_{ extrm {cause}}} and MIP effect { extstyle { extrm {MIP}}_{ extrm {effect}}} .Formally, Z t − 1 ∗ = { * ⁡ arg max Z t − 1 ( φ cause ( m t , Z t − 1 , MIP cause ) ) } { extstyle Z_{t-1}^{*}={operatorname {*} {arg ,max }_{Z_{t-1}},(varphi _{ extrm {cause}}(m_{t},,Z_{t-1},,{ extrm {MIP}}_{ extrm {cause}}))}} and Z t + 1 ∗ = { * ⁡ arg max Z t + 1 ( φ effect ( m t , Z t + 1 , MIP effect ) ) } { extstyle Z_{t+1}^{*}={operatorname {*} {arg ,max }_{Z_{t+1}},(varphi _{ extrm {effect}}(m_{t},,Z_{t+1},,{ extrm {MIP}}_{ extrm {effect}}))}} .The intrinsic cause-effect power of m t { extstyle m_{t}} is the concept's strength, and is given by: φ Max ( m t ) = φ ( m t , Z t ± 1 ∗ , MIP ) = min ( φ cause ( m t , Z t − 1 ∗ , MIP cause ) , φ effect ( m t , Z t + 1 ∗ , MIP effect ) ) { extstyle varphi ^{ extrm {Max}}(m_{t})=varphi (m_{t},,Z_{tpm 1}^{*},,{ extrm {MIP}})=min(varphi _{ extrm {cause}}(m_{t},,Z_{t-1}^{*},,{ extrm {MIP}}_{ extrm {cause}}),,varphi _{ extrm {effect}}(m_{t},,Z_{t+1}^{*},,{ extrm {MIP}}_{ extrm {effect}}))} In the XEMD, the 'earth' to be transported is intrinsic cause-effect power ( φ Max { extstyle varphi ^{ extrm {Max}}} ), and the ground distance between concepts A { extstyle A} and B { extstyle B} with cause repertoires A cause { extstyle A_{ extrm {cause}}} and B cause { extstyle B_{ extrm {cause}}} and effect repertoires A effect { extstyle A_{ extrm {effect}}} and B effect { extstyle B_{ extrm {effect}}} is given by EMD ( A cause , B cause ) + EMD ( A effect , B effect ) { extstyle { extrm {EMD}}(A_{ extrm {cause}},,B_{ extrm {cause}})+{ extrm {EMD}}(A_{ extrm {effect}},,B_{ extrm {effect}})} . Integrated information theory (IIT) attempts to explain what consciousness is and why it might be associated with certain physical systems. Given any such system, the theory predicts whether that system is conscious, to what degree it is conscious, and what particular experience it is having (see Central identity). According to IIT, a system's consciousness is determined by its causal properties and is therefore an intrinsic, fundamental property of any physical system. IIT was proposed by neuroscientist Giulio Tononi in 2004. The latest version of the theory, labeled IIT 3.0, was published in 2014. David Chalmers has argued that any attempt to explain consciousness in purely physical terms (i.e. to start with the laws of physics as they are currently formulated and derive the necessary and inevitable existence of consciousness) eventually runs into the so-called 'hard problem'. Rather than try to start from physical principles and arrive at consciousness, IIT 'starts with consciousness' (accepts the existence of consciousness as certain) and reasons about the properties that a postulated physical substrate would have to have in order to account for it. The ability to perform this jump from phenomenology to mechanism rests on IIT's assumption that if the formal properties of a conscious experience can be fully accounted for by an underlying physical system, then the properties of the physical system must be constrained by the properties of the experience.