The Semitic languages employed equivalents for many signs that were distorted or abbreviated to represent new values because the syllabic nature of the script as refined by the Sumerians was not intuitive to Semitic speakers. From the beginning of the Middle Bronze Age (20th century BC), the script evolved to accommodate the various dialects of Akkadian: Old Akkadian, Babylonian and Assyrian. In particular, the Old Assyrian cuneiform employed many modifications to Sumerian orthography. At this stage, the former pictograms were reduced to a high level of abstraction, and were composed of only five basic wedge shapes: horizontal, vertical, two diagonals and the "Winkelhaken" impressed vertically by the tip of the stylus. The signs exemplary of these basic wedges are: