Probability, 𝒯, that the environments of z = 1 ± 0.25, 2 ± 0.25, and 3 ± 0.25 LISA MBHBs have at least one galaxy of 10⁸ < M_stellar < 10⁹ M_⊙ featuring merger signatures. Black, red, and blue dots correspond to the values of 𝒯 when the population of 10⁸ < M_stellar < 10⁹ M_⊙ galaxies is divided according to galaxy merger ratios: all ratios, m_R > 0.2 (major mergers) and m_R > 0.01 (intermediate mergers), respectively. The error bars correspond to the 32th–68th percentile. Horizontal dashed lines highlight the values 𝒯 = 0.1, 0.5, and 0.9.