The view that human cognition may comprise two different types of processing, controlled and automatic, has been a theme in the psychology literature for over a century (e.g., James, 1890). This notion of dual processing has been prominent in the work of Richard Shiffrin and his students for the past 30 years. Shiffrin’s early work with Atkinson and Shiffrin (1968) detailed the role of controlled processing in studies of short-term memory and verbal learning. In the early 1970s, he and his students (Shiffrin & Gardner, 1972; Shiffrin, McKay, & Shaffer, 1976) performed attention studies indicating that multiple channels could be processed in parallel, a result that ran counter to much of the attention research of the time. Building on these earlier findings, Schneider and Shiffrin (1977) and Shiffrin and Schneider (1977) published a set of companion papers that set out the theoretical and empirical basis for much of the work on automaticity that has emerged in the ensuing decades (as illustrated by the over 4,800 citations of this work). There has followed an extended effort to develop an empirical and theoretical understanding of automatic and controlled processing.

Definition of automatic and controlled processing

The basic nature of automatic and controlled processing was laid out in our earlier papers. In Schneider and Shiffrin (1977), an automatic process was defined as the activation of a sequence of nodes that “nearly always becomes active in response to a particular input configuration,” and that “is activated automatically without the necessity for active control or attention by the subject” (p. 2). This ability for a process to occur in the absence of control and attention by the subject is perhaps the most salient feature of an automatic process, and was the basis for referring to such processing as “automatic.” In general, automatic processes “operate through a relatively permanent set of associative connections... and require an appreciable amount of consistent training to develop fully” (Schneider & Shiffrin, 1977, p. 2). An automatic attention response is a special type of automatic process that directs attention automatically to a target stimulus.

In contrast to automatic processes, Schneider and Shiffrin (1977, pp. 2–3) defined a controlled process as “a temporary sequence of nodes activated under control of, and through attention by, the subject.” Furthermore, controlled processes are “tightly capacity limited, but the costs of this capacity limitation are balanced by the benefits deriving from the ease with which such processes may be set up, altered, and applied in novel situations for which automatic sequences have never been learned.”

The contrast between automatic and controlled processing was initially studied using extended consistent mapping (CM) training. A consistent mapping task is one in which the response to the stimulus is consistent across extended periods of time (e.g., in a search task, the set of target stimuli is constant throughout the experiment). Under consistent mapping, automatic processes can develop slowly as repeated stimuli are attended to. Although there may be marked performance improvements even within the first few trials (Logan, 1992), full automaticity typically requires hundreds of trials to develop. In varied mapping (VM) training, the relationship of the stimulus to response mapping varies from trial to trial (e.g., in a search task, a stimulus that is assigned a given response on one trial is assigned a different response on the next trial). With varied mapping, the prior and current associations are incompatible, thereby precluding automaticity and the development of an automatic attention response.

Seven empirical phenomena of automatic and controlled processing

·      The first relevant phenomenon observed in this paradigm is that extended consistent training is required in order to develop automatic processing, while controlled processes can be established in a few trials and under varied mapping situations.

·      The second relevant phenomenon is that automatic processing is fast and parallel, while controlled processing is slow and serial.

·      A third important phenomenon is that automatic search requires little effort and can operate in high workload situations, whereas controlled processing requires substantial effort and interferes with other controlled processing tasks.

·      A fourth phenomenon is that automatic processing is rather robust to stressors.

·      A fifth phenomena (one that at the time we demonstrated it was so striking that it influenced the naming of “controlled” processing in our theory) is the difference in cognitive control that can be applied to automatic and controlled processes.

·      A sixth phenomenon is that the degree of learning is dependent on the amount and type of controlled processing, while there is little learning in pure automatic processing.

·      The seventh phenomenon is that the automatic attention response is dependent on the priority assigned to a stimulus itself, rather than on the context in which the stimulus occurs.

Advantages of two different processing modes

Dual processing mechanisms would likely not have evolved unless there were survival advantages to having both modes of processing. We propose that automatic and controlled processing are two qualitatively different forms of processing that provide complementary benefits. Our simulations suggest that a single process alone cannot provide both the fast learning of controlled processing and the high speed parallel robust processing of automatic processing. So, although it may be less parsimonious to assume two different modes of processing, we argue that there are sufficient survival advantages to a two-process system over a unitary architecture to have allowed a dual process system to evolve. The survival advantages to having both controlled and automatic processing are analogous to the non-overlapping and overlapping benefits of having rod and cone vision. With controlled processing: (1) the fundamentals of new skills can be acquired quickly (e.g., one trial learning to escape when a life threatening stimulus appears), (2) critical stimuli can be attended while ignoring normally relevant stimuli (attend to a child in a cross-walk while inhibiting the prepotent response to accelerate on a green light), (3) variable bindings that allow general operations to be applied to temporarily relevant stimuli can take place (e.g., after eating a novel food, search for it in the environment), (4) learning can be passed between individuals by instruction or observation (rather than shaping), and (5) goal-directed behavior can be planned and executed. However, due to the slow execution, high effort, and poor robustness of controlled processing, it can operate on only a small number of stimuli at any time, and any skill acquired during controlled performance may not be sufficiently robust to resist rapid decay or deterioration in the presence of stressors. Further, if a task requires the coordination of many sensory/motor inputs, the slow, resource limited nature of controlled processing will be a serious limitation (e.g., imagine trying to ski down a difficult slope using verbal rules to plan and execute motor movements). Despite taking a long time to acquire, automatic processing has the advantages of being robust under stress, leading to long-term retention of associated skills, and allowing many processes to occur in parallel.