Frishberg coined the word "classifier" in this context in her 1975 paper on American Sign Language.
[10] The handshapes in a two-handed classifier construction are signed in a specific order if they represent an entity's location.
The Dominance Condition states that the non-dominant hand cannot move and that its handshape comes from a restricted set.
[39] Hearing non-signers use forms similar to classifiers when asked to communicate through gesture.
[38] Certain classifier constructions may also, over time, lose their general meaning and become fully-fledged signs.
As a sign, the former classifier construction now conforms to the usual constraints of a word, such as consisting of one syllable.
[55] Allan described predicate classifiers as separate verbal morphemes that denote some salient aspect of the associated noun.
[57][58][59] In 1982, Supalla showed that classifier constructions were part of a complex morphological system in ASL.
they refer to a general semantic class of objects such as "thin and straight" or "flat and round".
[63] A fourth type, the body-part classifier, represents a human or animal body parts, usually the limbs.
[66][67][68] Schembri and colleagues similarly suggested in 2005 that classifier constructions are "blends of linguistic and gestural elements".
[69] Regardless of the high degree of variability, Schembri and colleagues argue that classifier constructions are still grammatically restrained by various factors.
Similar examples have been found in Digueño, which has morphemes that act like extension and surface classifiers in sign languages.
[74] It is now accepted that classifiers in spoken and signed languages are similar, contrary to what was previously believed.
[75] They both track references grammatically, can form new words and may emphasize a salient aspect of an entity.
Because classifier constructions are highly iconic, representational analyses argue that this form-meaning connection should be the basis for linguistic analysis.
This was argued because finite sets of morphemes or parameters cannot account for all potentially meaningful classifier constructions.
[82] A morphological analysis views classifiers as a series of morphemes,[83][60] and this is currently the predominant school of thought.
[84][85] In this analyses, classifier verbs are combinations of verbal roots with numerous affixes.
[8][87] For example, the fingertips in Swedish Sign Language can be bent in order to represent the front of a car getting damaged in a crash; this led Supalla to posit that each finger might act as a separate morpheme.
[86] Liddell found that to analyze a classifier construction in ASL where one person walks to another would require anywhere between 14 and 28 morphemes.
[60] Engberg-Pedersen disagreed with Supalla, arguing that the choice of handshape can fundamentally change how the movement is interpreted.
[95] However, signing children learn these constructions as part of a grammatical system, not as iconic representations of events.
[102] Other linguists claim that children as young as three years old can produce adult-like constructions,[102] although only with one hand.
[104] Slobin found that children under three years of age seem to "bootstrap" natural gesture to make learning the handshape easier.
[107] For spoken languages, describing spatial relationships only engages the left parietal cortex.
For sign languages, both the left and right parietal cortex are needed when using classifier constructions.
[109] In order to use certain classifier constructions, the signer must be able to visualize the entity and its shape, orientation and location.
[110] It has been shown that deaf signers are better at generating spatial mental images than hearing non-signers.
It has been observed in ASL poetry that skilled signers may combine classifiers and lexical signs.