We present an experimental and theoretical study which compares the phonon anomalies and the electronic gap features in the infrared response of the weakly coupled two-leg-ladders in Sr 14-x CaxCu24O41 (SCCO) with those of the underdoped high-T ( c ) superconductor YBa2Cu3O 6+x 2 planes) of YBCO. We further confirm that an insulator-like pseudogap develops in the a-axis conductivity of SCCO which closely resembles that in the c-axis conductivity of YBCO. Most surprisingly, we find that the c-axis conductivity (field along the legs of the ladders) of SCCO is strikingly similar to the in-plane one (field parallel to the CuO2 planes) of YBCO. Notably, in both cases a dip feature develops in the normal state spectra that is connected with a spectral weight shift toward low frequencies and can thus be associated with precursor superconducting pairing correlations that are lacking macroscopic phase coherence. This SCCO-YBCO analogy indicates that collective degrees of freedom contribute to the low-energy response of underdoped high T ( c ) cuprates and it even suggests that the charges in the CuO2 planes tend to segregate forming quasi-one-dimensional structures similar to the two-leg ladders, as predicted for the stripe-scenario or certain intertwinned states.