Studies have shown that individual differences in inner speech propensity may impact how fast participants recognize objects. In addition, inner speech has been suggested to support abstract thinking and metacognition. In the first part of this study, we provide a means to assess individual differences in inner speech in German-speaking samples by validating a German version of the Internal Representations Questionnaire (IRQ), an instrument measuring different modes of thinking, including the tendency to experience inner speech, termed Internal Verbalization (IV). Results from validity and reliability analyses will be discussed in view of the original IRQ. Then, we examine the effects of IV in a word-picture verification task where participants match words followed by pictures and vice-versa, with cue-target similarity varying continuously in phonological and semantic dimensions. Following previous reports of a role for inner speech in object recognition, we predict slower responses in phonologically similar trials and faster responses in semantically similar trials for individuals with higher IV. Furthermore, we examine the effects of IV in a task where participants select images in contexts with varying degrees of abstract thinking demands and then indicate how confident they are in their selection. Following studies associating linguistic abilities with abstract thought and metacognition, we predict for higher IV shorter times to select a picture in abstract trials and to indicate response confidence. The results will help assess the predictive validity of the German IRQ and will be discussed in light of previous evidence connecting inner speech and cognition.