Neglected cases of rightward movement. When wh-phrases and negative quantifiers go to right

We show that sign languages admit genuine cases of rightward movement in the domain of wh-phrases and negative quantifiers, instantiating the mirror image of spoken languages in which wh-phrases and negative quantifiers overtly move leftward. The pattern emerging from Italian Sign Language (LIS), American Sign Language (ASL) and Indo-Pakistani Sign Language (IPSL) opens intriguing questions concerning the role of language external factors influencing the final shape of languages at the articulatory-perceptual interface. According to the account offered here, language external factors, in accordance with the Processing-to-Grammar Correspondence Hypothesis, actively interact with language specific rules and configurations, determined by the parameters of Universal Grammar.