Note that the Wigners formula_37 and formula_39 look at the laboratories formula_80 and formula_81 from the outside, i.e., they are assumed to see the labs as perfectly isolated. Hence, they model it as a pure state superposition up to the time they themselves have measured their lab. However, even though lab formula_81 stays isolated as a system, the extended Wigner’s friend experiment is constructed such that some information about the state of formula_1 is accessible to outsiders. This is achieved by letting the state of formula_1 depend on the outcome of formula_36's measurement.