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Article Excerpt
INTRODUCTION
The term situation awareness (SA) has been highlighted in the aviation world because of its prominent role in flight operations. Although it has been considered an essential prerequisite for the safe operation of aircraft, the term is inconsistently used in the domain of aviation. Its use is most often based on an intuitive understanding, and a commonly accepted definition is not provided. To fill this gap, aviation psychologists have focused on the cognitive components of SA because of the increasingly cognitive nature of the tasks operators should perform (Durso & Gronlund, 1999; Endsley, 1995b; Sarter & Woods, 1991 ; Wickens, 1999). Thus researchers in aviation psychology have sought to determine the cognitive requirements that constitute SA. Previous studies in the aviation domain have provided important support for the centrality of memory processes in SA, addressing the nature of individual differences in using memory processes during SA (Carretta, Perry, & Ree, 1996; Endsley & Bolstad, 1994; Gugerty & Tirre, 2000; Joslyn & Hunt, 1998; O'Hare, 1997). The objective of the present research was to determine the locus of individual differences in pilot ability to accommodate the demands that SA imposes on memory. Because experience may enhance SA by reducing the amount of mental resources required for building and maintaining SA, we examined the role of memory processes in SA as a function of pilot expertise.
MEMORY PROCESSES IN SITUATION AWARENESS
The role of memory is viewed as central to performing tasks that require dynamic and complex processing, such as SA (Durso & Gronlund, 1999; Endsley, 1995b). The content relevant to SA (e.g., tasks, systems, or hazards) is processed and resides in memory (Wickens, 1999). The accuracy of SA depends also on memory in which incoming information is integrated into coherent interpretation and prediction of aircraft status. Because of the importance of memory components of SA, many SA researchers have focused on the role of memory in a variety of task domains, including air traffic control (e.g., Gronlund, Ohrt, Manning, Dougherty, & Perry, 1998), driving (e.g., Gugerty, 1997) and instrument flight (e.g., Doane, Sohn, & Jodlowski, 2004).
In order to understand memory processes in SA, it is necessary to understand the construct of SA. The spirit of most definitions of SA can be incorporated into Endsley's (1995b) information processing view (Durso & Gronlund, 1999; Jones & Endsley, 2000; Wickens, 1999). Endsley's (1995b) view defines three levels of SA in terms of component cognitive processes. The first level involves perceiving environmental elements, such as other aircraft, terrain, system status, and warning lights. The second level involves information integration, a process of activating long-term memory (LTM) knowledge structures in order to organize the perceived situation elements into meaningful and recognizable configurations. The third level includes processes that enable projection of future flight status.
This third level of SA uses the goal-relevant activated knowledge structures formed in the second level of SA to predict the status of the aircraft. The accuracy of SA is a function of activating LTM knowledge structures that facilitate the integration of environmental information and result in a coherent interpretation of the current and future flight status. Recent work suggests that the integration of environmental information takes place in working memory (WM; Durso & Gronlund, 1999; Endsley & Garland, 2000). In summary, SA in Endsley's (1995b) view involves memory processes that dictate whether the resulting level of awareness will facilitate or detract from pilot performance.
RESEARCH ON MEMORY PROCESSES IN SITUATION AWARENESS
Many SA researchers suggest that understanding component processes is crucial to understanding failures in SA (e.g., Durso & Gronlund, 1999; Endsley, 1995b; Sarter & Woods, 1991). Adams, Tenney, and Pew (1995) suggested that componential analyses would address the practical need for the ability to predict failures in SA. As an example, they described a list of indicators of incomplete SA that was devised to help pilots detect SA problems.
Recent research suggests that componential analyses of memory processes are useful in predicting SA failures (see Durso & Gronlund, 1999, for a complete review of additional componential research). For example, in a study of U.S. Air Force F-15 pilots, Carretta et al. (1996) showed that cognitive factors such as verbal working memory, spatial working memory, spatial reasoning, and divided attention were the reliable predictors of SA after controlling for the effects of flight experience. Although Carretta et al. used cognitive factors based solely on WM as predictors of SA, Stokes, Kemper, and Kite (1997) used LTM-based knowledge representations as well as WM-based information processing abilities to predict decisionmaking performance on a simulated flight situation. Stokes et al. found that both LTM-based knowledge representation measures and WM-based spatial memory measures were predictive of flight decision making.
Although the previous studies pointed to memory processes as important components of SA, the respective roles of WM and LTM and their relationship in the context of SA have yet to be determined clearly. As an attempt to address this issue, the present research examined main and interactive effects of WM and LTM processes on SA performance in instrument flight tasks using theoretical analysis based on cognitive theories developed in a variety of domains (e.g., Baddeley, 1986; Ericsson & Kintsch, 1995; lust & Carpenter, 1992; Larkin, McDermott, Simon, & Simon, 1980; Shah & Miyake, 1996; Sohn & Doane, 1997). In testing the validity of possible accounts based on the current cognitive theories, this research provides an insight into the cognitive requirements that constitute SA and the effective training methods that optimize acquisition and maintenance of SA.
PRESENT RESEARCH
Research Objective
The specific research question addressed was whether individual capacity to maintain information in WM, individual ability to construct and use LTM retrieval structures, or both, are the loci of SA performance differences among pilots of varying expertise. This objective was achieved by analyzing pilot SA performance for expert and novice groups in the context of cognitive theories. Of interest was the ability of contrasting theories to explain and predict performance differences in flight SA.
The capacity theory of WM proposes that the locus of individual differences in performing a complex task is the domain-general fixed capacity to compute and maintain presented information in WM (e.g., Daneman & Carpenter; 1980; Just & Carpenter, 1992; Shah & Miyake, 1996). This capacity is assumed to be inherently different across individuals. Alternatively, the long-term working memory (LT-WM) theory proposes that the locus of the differences is the acquired domain-specific skill to encode the presented information efficiently in accessible form in LTM (e.g., Ericsson & Delaney, 1999; Ericsson & Kintsch, 1995). This account of memory process is referred to as LT-WM because it postulates a mechanism for extending WM that requires skilled use of storage in and retrieval from LTM. The LT-WM theory proposes that individuals can acquire retrieval structures through extensive knowledge built up from experience in a particular domain and can use them to dynamically increase the functional capacity of WM. Thus our research objective was accomplished by devising measures of WM capacity and LT-WM skill and then comparing the measures' ability to predict the differences in performance on SA tasks.
Overview of Experiment
The present experiment consisted of three tasks. First, the span tasks of Daneman and Carpenter (1980) and Shah and Miyake (1996) were modified to measure individual WM capacity. Many researchers hypothesize separate WM resources for different modalities of cognitive processes (e.g., Daneman & Tardif, 1987; Shah & Miyake, 1996). Based on this hypothesis, the span tasks assessed individual WM capacity for computation and storage of spatial and verbal information.
Second, a situation recall task analogous to the Chase and Simon (1975) chess experiment was devised to measure individual pilots' LT-WM skill. Their experiment showed that chess masters were able to reconstruct more chess pieces on a board than were novices if the pieces were originally arranged in a meaningful game position. In contrast, if the pieces were placed in a random configuration, chess master performance fell to novice levels. In the present...
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