Glottalization, preaspiration and gemination in English and Scandinavian

Docherty et alii have "noted that several sociolinguistic accounts have shown a sharp distinction between the social trajectories for glottal replacement as opposed to glottal reinforcement, which have normally been treated by phonologists as aspects of 'the same thing'. It may therefore not always be appropriate to treat the two phenomena as manifestations of a single process or as points on a single continuum (presumably along which speakers move through time). From the speaker’s point of view (as manifested by different patterns of speaker behaviour) they appear as independent phenomena" (1997: 307).