This article reports the findings of a causal-comparative study with spoken language (primarily conference) and signed language (primarily public service) interpreting students carried out at four institutions in the European Union in 2008. The study was built on two previous investigations of essential characteristics, as reported by interpreting students and their professors, to measure these characteristics with standardized performance and motivation tests. It grouped participants as “entry-level” or “advanced” depending upon their prior experience in simultaneous interpreting coursework. The study documented cognitive and motivational scores of spoken language (SP) and signed language (SL) interpreting students at both levels, using a computerized neuropsychological screening test and an achievement motivation instrument. Significant differences between the SP and SL students were found in the areas of visual memory, concentration, and internality (belief that success is due to internal causes), and between the advanced and entry-level students in the areas of concentration and the eagerness to learn new concepts in the absence of external rewards.