Table 1.

α₁ = effect of vehicle

α₂ = effect of morphine

β₁ = effect of mild stress

β₂ = effect of severe stress

γ₁ = interaction effect of vehicle, α₁, with mild stress, β₁, probably zero

γ₂ = interaction effect of morphine, α₂, with β₁+γ₁, probably negligible

γ₃ = interaction effect of α₁+γ₁ with severe stress, β₂

γ₄ = interaction effect of α₂+γ₂ and β₂+γ₃