Figure 3.

Binary decisions. (a) Binary choice landscape. In the starting condition, Signal 1, cells are in a progenitor state corresponding to the middle basin of the landscape. Exposure to Signal 2 results in the disappearance of the central basin and the bottom ridge and cells transition into State B following the slopes of the new landscape. (b) Two parameters p₁ and p₂ govern the landscape in (a). Bifurcations occur when these parameters are on the black curves in p₁, p₂-space. Crossing one curve results in cells transitioning to A; crossing the other, cells transition to B. (c) Binary flip landscape. Cells start in the progenitor state P which corresponds to a shallow basin. Noise is sufficient for cells to transition into the more committed states and they follow the escape route (red) towards state A when exposed to Signal 1. In response to Signal 2 the escape route flips towards B and cells transition towards B. (d) The landscape in C is also governed by two parameters. The progenitor attractor is destroyed when the parameters are on the black curve and the flip occurs when the parameters are on the purple curve.