In summary, considerable controversy and research have been generated from the automatic/effortful distinction. Hasher and Zacks (1979) initially stated that all manipulations (e. g. , practice, individual differences such as age, orienting instructions) must produce null effects in order to satisfy the criteria that a process is "automatic. " However, Zacks et al. (1984) have more recently noted that automatic processes may range in degree from relative insensitivity to task and subject variables (e. g. , frequency processing) to those that are more vulnera- ble to disruptive effects (e. g. , temporal processing). A review of the literature reveals that individuals are sensitive to frequency information even if manipUla- tions alter the slope of the judgments. Perhaps the application of dual-task metho- dology to the measurement of capacity demands will be useful in classifying processes along an attentional continuum. Moreover, there has been a tendency to dichotomize automatic/effortful processes rather than to characterize them as ranging from low to high attentional demands.
Recent evidence (Maki & Ostby, 1987) suggests that attention may be important only in the initial (early) stages of processing frequency information. Therefore, a major difference that may emerge between automatic and effortful processing could be the degree of sus- tained attention required from individuals. In the following section, we review the findings obtained in the application of the automatic/effortful framework to the elderly and neurological/psychiatric populations.