“…While there were group differences in the extent to which deaf participants could provide verbal labels for different category groupings, these differences disappeared once academic achievement was controlled for (Kates, Kates, Michael, & Walsh, 1961; see also Rosenstein, 1960). For Furth -a researcher known for claiming that deaf cognition fundamentally lacked language (Furth, 1966) -findings such as these indicated that concept processing abilities were intact in people who are deaf, and clearly separable from any difficulties with language (see Vernon, 1967, for a similar conclusion) 15 .…”