PATTERNS OF EXCITATION AND INHIBITION IN PICTURE NAMING

Previous work has demonstrated that, if a series of objects is named s uccessively under speeded naming instructions, then responses from ear ly trials can re-occur as errors to later objects. This illustrates th e competitive nature of object naming, and the perseverative effect is due to the higher activation levels within the object-naming system o f early named objects relative to new, to-be-named objects. Campbell a nd Clark (1989) have demonstrated similar interference effects in simp le arithmetic problems, and they examined errors with respect to the f requency with which they match responses on previous trials at various intervals (lags). They found that errors relating to the immediately preceding trial were reduced, and they argue that this is due to a tem porary inhibitory effect. The experiment reported here adopted the met hods and statistical procedures used by Campbell and Clark to investig ate the possibility of a similar inhibitory effect in picture naming. Subjects named 30 pictures of animals under speeded naming instruction s, and the errors were examined in relation to the lag between error a nd original response. The interference effects due to excitation remai ning in the system were confirmed, but these errors related only to re sponses several trials earlier. No errors related to the immediately p receding response were observed, suggesting a brief inhibitory effect. The data therefore confirm those of Campbell and Clark on arithmetic errors, suggesting that both excitatory and inhibitory processes may a lso co-exist in picture naming. Possible mechanisms for inhibition and its locus within the system are discussed.