It has been observed that there is a systematic detection of weak pressure stimulated electric currents (PSC) in polycrystalline and amorphous solids during or after an application of mechanical stress upon them. An interpretation of the mechanisms governing the electrical behaviour of solid structures when they undergo uniaxial stress tests is presented. In numerous experiments, repetitive stress loadings and unloadings have been conducted, the corresponding PSC have been recorded, and the behaviour of the material is interpreted with respect to PSC emission. The dominant conclusion is that the behaviour of the solid depends on the overall stress it has suffered and that PSC is related with a memory effect which associates current emission with the previous history of the sample.