Head movement constraint

Head Movement Constraint is a constraint originally formulated in Travis (1984:131):

(i) An X0 may only move into the Y0 which properly governs it

The HMC basically places a limit on the distance over which a head may be moved (head movement). In effect, the HMC prohibits skipping a governing head position, as in (ii): buy moves to COMP in disregard of its being properly governed only by the I0 will.

(ii) * [CP What [C buyi] [IP John [I will] [VP ti]]]?

Recently, it has been argued that the HMC can be derived from more general principles, such as the ECP.

Link
Utrecht Lexicon of Linguistics

Other languages
Chinesisch 中心语移位约束定律 German Kopf-Bewegungsbeschränkung Französisch restriction du mouvement de la tête