Pick-up signals from Langmuir probes have been measured in the boundary of the TEXTOR tokamak during discharges with different transport properties namely attached, detached and electrically induced H-mode plasmas. These signals have then been analysed with respect to their dimensionality. The dimensionality is found to be high for attached plasmas, even higher for the H-mode discharges induced by polarization and it is low for detached plasmas. It is found that the dimensionality depends on the radial position of the probes and on the above discharge conditions. Changes in the dimensionality are accompanied by changes in the frequency spectra of the pick-up signals and also by changes in such plasma parameters as rotation speed, rotation shear and radial particle and heat transport.