Vinay and Darbelnet took to Saussure's original concepts of the linguistic sign when beginning to discuss the idea of a single word as a translation unit.
However, Russian scholar Leonid Barkhudarov[2] stated that, limiting it to poetry, for instance, a translation unit can take the form of a complete text.
In this point of view we can consider the concept of the think-aloud protocol, supported by German linguist Wolfgang Lörscher: isolating units using self-reports by translating subjects.
Records of keystrokes and eye movements allow to investigate these mental constructs through their physical (observable) behavioral traces in the translation process data.
Empirical Translation Process Research has deployed numerous theories to explain and models the behavioral traces of these assumed mental units.