Lexical decision in Parkinson's disease: A comment on Spicer, Brown, and Gorell (1994), and McDonald, Brown, and Gorell (1996)

Recent semantic priming investigations conducted by Spicer, Brown and Gorell (1994) and McDonald, Brown and Gorell (1996) reported hyperpriming in persons with Parkinson's disease (PD) and provided evidence supporting impaired set-shifting as the underlying cause. This paper discusses notable priming behaviours exhibited by the normal control groups employed by Spicer and McDonald and colleagues. The argument is developed that these studies only measured attention-dependent semantic processing and, therefore, their results do not speak to issues of automatic semantic activation in PD as originally proposed by Spicer et al. nor to putative deficits in set-shifting as proposed by McDonald et al. The implications for future priming research in PD are also discussed.