Degree comparatives express gradation between two or more items. They involve an adjectival predicate [Syntax - 2.1.1.]. This adjectival predicate is used to compare the subject of a first clause to the subject of a second clause [Syntax - 3.6].
Degree comparatives are expressed in two allomorphic variations the use of which depend on the nature of the adjectival predicate used. The first allomorphic variant is the use of lexical degree signs, which are also called, parameter markers [Syntax - 3.6]. Two of these parameter marker signs are more and most, which express relative and absolute superiority. These markers are coarticulated with raised eyebrows and eye opening.
Another parameter marker is less which expresses relative but not absolute inferiority. This marker is coarticulated with eyebrow furrowing and eye squint.
The second morphological variant used in expressing degree comparatives is incorporation of the degree into the predicate sign, namely expressing bigger rather than more+big. As can be seen from the examples below, these comparative signs consist of both manuals and non-manuals. For the manual part the comparative morpheme is incorporated with the adjectival predicate. We illustrate this way of expressing comparison with two signs below. There is a semantic difference between these two signs and this is reflected in the way they are expressed. In the expression of bigger, the movement is outward but in the expression of thinner, the movement is inward. For the non-manual part, the eyes are wide open with bigger and the eyebrows are raised whereas the eyes are squinted and the eyebrows are furrowed for thinner.
bigger thinner
(r.f. รzsoy& Kaลฤฑkara 2018b: 22)