Single Pilot Operations in Domestic Commercial Aviation.

OBJECTIVE: To provide an overview of concepts of operation for single pilot operations (SPO) and a synthesis of recently published work evaluating these concepts. BACKGROUND: Advances in technology have made it possible for a commercial aircraft to be flown by a single pilot under normal conditions, and research is being conducted to examine the feasibility of implementing SPO for commercial aviation. METHOD: Context leading up to the consideration of SPO for commercial flight is provided, including the benefits and challenges. Recent studies examining issues relating to automation, operations, and communications in the SPO context are presented. RESULTS: A number of concepts have been proposed and tested for SPO, and no one concept has been shown to be superior. Single pilots were able to successfully resolve off-nominal scenarios with either the ground-support or cockpit-automation tools examined. However, the technologies developed in support of these concepts are in prototype forms and need further development. CONCLUSION: There have been no obvious "show stoppers" for moving toward SPO. However, the current state of research is in its initial stages, and more research is needed to examine other challenges associated with SPO. Moreover, human factors researchers must continue to be involved in the development of the new tools and technologies to support SPO to ensure their effectiveness. APPLICATION: The research issues highlighted in the context of SPO reflect issues that are associated with the process of reducing crew members or providing remote support of operators and, more generally, human interactions with increasingly autonomous systems.

Is attention needed for word identification? Evidence from the Stroop paradigm.

One of the most robust findings in attention research is that the time to name a color is lengthened markedly in the presence of an irrelevant word that spells a different color name: the Stroop effect. The Stroop effect is found even when the word is physically separated from the color, apparently indicating that words can be read outside the focus of spatial attention. The present study critically evaluated this claim. We employed several stringent measures within a Stroop paradigm to prevent participants from attending to the irrelevant words (e.g., limiting exposure duration to prevent attention capture). Nonetheless, residual Stroop effects were obtained for both color words and semantic associates (e.g., sky to blue). These data suggest that lexical processing can sometimes occur outside the focus of spatial attention.

Forty-five years after Broadbent (1958): still no identification without attention.

According to D. E. Broadbent's (1958) selective filter theory, people do not process unattended stimuli beyond the analysis of basic physical properties. This theory was later rejected on the basis of numerous findings that people identify irrelevant (and supposedly unattended) stimuli. A careful review of this evidence, however, reveals strong reasons to doubt that these irrelevant stimuli were in fact unattended. This review exposed a clear need for new experiments with tight control over the locus of attention. The authors present 5 such experiments using a priming paradigm. When steps were taken to ensure that irrelevant stimuli were not attended, these stimuli produced no priming effects. Hence, the authors found no evidence that unattended stimuli can be identified. The results support a modern version of Broadbent's selective theory, updated to reflect recent research advances.

Even frequent and expected words are not identified without spatial attention.

Previous studies have disagreed about the extent to which people extract meaning from words presented outside the focus of spatial attention. The present study examined a possible explanation for such discrepancies inspired by attenuation theory: Unattended words can be read more automatically when they are expected within a given context (e.g., due to frequent repetition). We presented a brief prime word in lowercase, followed by a target word in uppercase. Participants indicated whether the target word belonged to a particular category (e.g., "sports"). When we used a visual cue to draw attention to the location of the prime word, it produced substantial priming effects on target responses (i.e., especially fast responses when the prime and target words were identical or from the same category). When prime words were not attended, however, they produced no priming effects. This finding replicated even when there were only four words, each repeated 160 times during the experiment. It appears that very little word processing is possible without spatial attention, even for words that are expected and frequently presented.

Space, object, and task selection.

Within the field of selective attention, two separate literatures have developed, one examining the effect of selection of objects and another examining the effect of selection of features. The present study bridged these two traditions by examining the compatibility effects generated by two features of attended and unattended nontarget (foil) stimuli. On each trial, participants determined either the identity or the orientation of a visual stimulus. Spatial attention was controlled using cues (presented prior to the target frame) designed to involuntarily capture attention. We independently manipulated the stimulus dimension the participants prepared for and the stimulus dimension on which they actually executed the task. Preparation had little influence on the magnitude of compatibility effects from foil stimuli. For attended stimuli, the stimulus dimension used in executing the task produced large compatibility effects, regardless of whether that dimension was prepared. These and other compatibility effects (e.g., Stroop effects) are discussed in relation to an integrative model of attentional selection. The key assumptions are that (1) selection occurs at three distinct levels (space, object, and task), (2) spatial attention leads to semantic processing of all dimensions, and (3) features do not automatically activate responses unless that object is selected for action.