THE LIVING NONLIVING DISSOCIATION IS NOT AN ARTIFACT - GIVING AN A-PRIORI IMPLAUSIBLE HYPOTHESIS A STRONG TEST

Some brain-damaged patients seem to have more difficulty retrieving in formation about living things than about nonliving things. Does this r eflect a distinction between two different underlying brain systems sp ecialised for knowledge of living and nonliving things, or merely a di fference in the difficulty of retrieving these two kinds of knowledge from a single semantic memory system? Two recent articles (Funnell & S heridan, 1992; Stewart, Parkin, & Hunkin, 1992) have concluded the lat ter, on the basis of experiments in which various determinants of nami ng difficulty were matched for living and nonliving things and the pre viously observed dissociation was found to vanish. We argue that these null effects are due to insufficient power, and that knowledge of liv ing things can be selectively impaired. In support of this, we use the same stimulus materials, design, and data analysis as did Funnell and Sheridan (1992), with two different subjects having the same aetiolog y and general behaviour in the domain of semantic memory, and show tha t: (1) when, like the authors of these articles, we use only a single replication of each item, no effect is found, and (2) when we use more replications of the same items, highly significant differences betwee n living and nonliving items emerge, for each of two subjects. Finally , we contrast and evaluate the three available hypotheses for explaini ng living/nonliving dissociations, and on the basis of the results pre sented here and other data, tentatively endorse one of them.