Evaluating design proposals for complex systems with work domain analysis.

In this paper we propose a new framework for evaluating designs based on work domain analysis, the first phase of cognitive work analysis. We develop a rationale for a new approach to evaluation by describing the unique characteristics of complex systems and by showing that systems engineering techniques only partially accommodate these characteristics. We then present work domain analysis as a complementary framework for evaluation. We explain this technique by example by showing how the Australian Defence Force used work domain analysis to evaluate design proposals for a new system called Airborne Early Warning and Control. This case study also demonstrates that work domain analysis is a useful and feasible approach that complements standard techniques for evaluation and that promotes a central role for human factors professionals early in the system design and development process. Actual or potential applications of this research include the evaluation of designs for complex systems.

Selective attention and interhemispheric response competition in the split-brain.

The interfering effect of an unattended stimulus on processing of an attended item was studied in a single split-brain participant (LB) and in normal controls. Pairs of letters were presented to the left visual field (LVF), right visual field (RVF), or bilaterally. Participants attended to the rightmost letter while attempting to ignore the leftmost letter. Responses associated with the attended and to-be-ignored letters could be compatible or incompatible. Manual response latencies were generally slower on Response Incompatible compared to Response Compatible trials. Notably, LB displayed this effect on Bilateral trials, where target and distractor were presented to opposite visual fields. LB was unable to perform a same-different matching task with bilateral letter stimuli, but was able to name bilateral letters accurately. Hence, in the bilateral condition, the ability to cross-compare letters was dissociated from attentional interference and from letter naming. Implications of these findings are discussed.

Same/different judgements about the direction and colour of apparent-motion stimuli after commissurotomy.

One subject with complete forebrain commissurotomy (L.B.), another with posterior callosotomy (D.K.) and 6 normal controls were tested for their ability to make same/different judgements about the direction (Experiment 1) and colour (Experiment 2) of apparent-motion stimuli. In the first experiment, all of the subjects were able to judge whether the direction of apparent motion of two stimulus sequences was the same or different, regardless of whether the two sequences were presented unilaterally or bilaterally. In the second experiment, however, L.B. was unable to judge whether the colours of two lights comprising an apparent motion sequence were the same or different when the two lights were presented bilaterally although he was able to do so when both lights were in the same visual field. D.K. was able to make the discrimination on both bilateral and unilateral presentations but he performed more poorly in the bilateral condition than in either visual field. The control subjects performed consistently in all three locations. Given that same/different judgement tasks are a rigorous test of interhemispheric integration, the results indicate that the ability to discriminate apparent motion across the retinal midline is intact in split-brained subjects. Furthermore, the results support a dissociation in the interhemispheric integration of the direction and colour of apparent-motion stimuli after commissurotomy.

Perception of apparent motion of colored stimuli after commissurotomy.

One subject with complete forebrain commissurotomy (L.B.), another with posterior callosotomy (D.K.), and eight normal controls were presented with successive pairs of red and/or green lights, on either side of the retinal midline and within the left and right visual fields. All of the subjects could discriminate the direction of apparent motion in all three locations, although L.B. was poorer on bilateral than unilateral presentations. Moreover, on bilateral presentations, L.B. was significantly poorer at identifying the color of the first light than the color of the second light. In contrast, D.K., like the control subjects, was equally good at identifying the color of either light. These and other results provide evidence that a subcortical shift in attention enables L.B. to discriminate the direction of apparent motion across the midline. On the other hand, a more robust mechanism involving the middle temporal area of the cortex must be responsible for tracking motion in D.K. and the control subjects. On the basis of these findings, it is suggested that the superior colliculus may contribute to direction sensitivity in the middle temporal area by mediating shifts in spatial attention.

Perception of apparent motion across the retinal midline following commissurotomy.

One subject (L.B.) with complete forebrain commissurotomy, another (D.K.) with posterior callosotomy, and 12 normal controls, were shown either single lights, simultaneous pairs, or successive pairs, presented either within the left or right visual fields or bilaterally. Regardless of location, all subjects scored at or near ceiling in discriminating: (1) simultaneous pairs from single lights, (2) successive pairs from single lights, (3) simultaneous pairs from successive pairs, and (4) leftward succession from rightward succession. However, with bilateral presentation, L.B. was often slow to respond to successive lights, and his accuracy in detecting bilateral succession deteriorated when successive presentations were intermixed with simultaneous pairs and single lights. These and other results suggest that three mechanisms may contribute to the discrimination of apparent motion: the detection of simultaneous events, a subcortically mediated switch in attention from first to second location, and cortical tracking between locations. Cortical tracking across the midline is incapacitated following complete forebrain commissurotomy.