Amplitude of the Balmer break as a function of the UV slope for the objects in our sample (black squares and error-bars) compared to templates at different ages (continous lines: 0.01 Gyr to 1 Gyr from bottom to top) and star-formation histories: exponentially declining SFH (τ = 0.3 Gyr, bottom panel), constant SFH (central panel), exponentially increasing SFH (τ = 0.3 Gyr, top panel). The Balmer colour is defined as H160-0.5 × (K+3.6 μm) for objects and templates at z > 3.4, and J125-0.5 × (K+3.6 μm) for lower redshifts. The reddening vector in this plot is parallel to the displayed model tracks.