A model for Subjective Grouping in Typewriting

Timing in the Motor Programming of Typing

In developing a theory of motor programming of skilled performance it has been suggested that an abstract, structural representation in the program specifies both a sequence of responses and expressive features of the sequence, such as timing, stress and intonation, which are mapped separately into the response output. In the case of typing, which does not require expressive features, it has previously been assumed that response timing is governed more simply by a timekeeper providing a stochastically regular beat. Two sets of specially constructed texts were given to a fast typist and the results support the idea that skilled typing is paced by a regular beat. They also show that there were systematic rhythmic departures from the beat, which arose from contingencies of keyboard movement but were not the simple consequences of these; rather they may be regarded as structured anticipations of the contingencies, and as such are analogous to the expressive features of speech and playing music.

Learning while Typing

Subjects representing two different levels of skill in typewriting participated in an experiment concerning higher mental activities in connection with typewriting. Understanding and learning of the text typed was facilitated simply by the instruction: “Think of what you are typing!”. The improvement in learning was accompanied neither by increase in time nor in mean number of errors.

Coding Factors in Transcription

Two experiments looked at aspects of stimulus grouping by trainee typists and tested for the possibility of response grouping. Manipulating text preview indicated that typing speed declined if the next word was not wholly on display but, conversely, there was little gain if it was displayed much in advance of its being typed. Some of the effect of practice was specific to the words actually typed: words not presented during practice were typed slower than practised ones; others given reinforced practice were typed quicker than the rest. An analysis of response latencies provides evidence that response grouping sometimes occurred.

Control Processes in Typing

Recent studies have used errors in speech and typing as a source of evidence for the hypothesis put forward by Lashley (1951) that response is hierarchically organized. The present study continues this line of inquiry on typing, using both the form of the error and its latency as data. Earlier models to account for the latency of typing have postulated two stages of output processing and with a slight modification to the notion of a stage it is shown that they can also account for the error data. Suggestions are made on the nature of codes represented in each stage and on the aetiology of errors. An analysis of response latency in the vicinity of errors supports a conclusion that error detection is very rapid and the (inferred) incidence of detection suggests that it is based upon a comparison process rather than an estimate of response likelihood.

Overlapping mental operations in serial performance with preview

Dual-task research has revealed a response-selection bottleneck: response selection cannot occur simultaneously in two different tasks, though perceptual processing may overlap response selection (Welford, 1952; Pashler & Johnston, 1989). In serial performance with preview, the same task is performed repeatedly, but stimuli are available well before response. Does the dual-task bottleneck limit the rate of responding in this situation, despite the fact that task set need not change? Four experiments examined manual responses to letters, varying stimulus preview. Preview increased RTs for the first response and reduce the subsequent inter-response intervals (IRIs). Preview also reduced the effect of visual intensity and response duration on IRIs, whereas effects of stimulus-response mapping variables were unchanged. These results indicate that the response-selection bottleneck limits serial performance, just as it limits concurrent performance of two unrelated tasks. This implies that the response-selection bottleneck is not caused by the need to switch task set.

Serial Checking of Letter Targets

A total of 24 subjects quickly and correctly checked target Zs in a letter array in order of location. Zs were embedded in angular, round, and mixed angular and round nontarget letters. Checking rate decreased as visual difficulty increased but increased as the number of letters interposed between adjacent targets increased. Time per letter computed for a span, which included a target and interposed letters preceding the target, varied as a function of checking the order of targets. The trend of the variation in rate differentiated among spans of different length and was also influenced by the visual difficulty. This differentiation might represent subject's unintended strategy for the task.