Robert S. McCann

On the association between connectionism and data : are a few words necessary?

Parallel distributed processing models represent a new and exciting approach to the study of visual word recognition in reading. Seidenberg and McClellands (1989) model is examined because the strongest and widest claims for the viability of a connectionist account of visual word recognition have been made on the basis of their model.

Taxiway Navigation and Situation Awareness (T-NASA) System: Problem, Design Philosophy, and Description of an Integrated Display Suite for Low-Visibility Airport Surface Operations

An integrated cockpit display suite, the T-NASA (Taxiway Navigation and Situation Awareness) system, is under development for NASAs Terminal Area Productivity (TAP) Low-Visibility Landing and Surface Operations (LVLASO) program. This system has three integrated components: Moving Map -- track-up airport surface display with own-ship, traffic and graphical route guidance; SceneLinked Symbology -- route/taxi information virtually projected via a Head-up Display (HUD) onto the forward scene; and, 3-D Audio Ground Collision Avoidance Warning (GCAW) system -- spatially-localized auditory traffic alerts. In this paper, surface operations in low-visibility conditions, the design philosophy of the T-NASA system, and the TNASA system display components are described.

The role of spatial attention in visual word processing

Subjects made lexical decisions on a target letter string presented above or below fixation. In Experiments 1 and 2, target location was cued 100 ms in advance of target onset. Responses were faster on validly than on invalidly cued trials. In Experiment 3, the target was sometimes accompanied by irrelevant stimuli on the other side of fixation; in such cases, responses were slowed (a spatial filtering effect). Both cuing and filtering effects on response time were additive with effects of word frequency and lexical status (words vs. nonwords). These findings are difficult to reconcile with claims that spatial attention is less involved in processing familiar words than in unfamiliar words and nonwords. The results can be reconciled with a late-selection locus of spatial attention only with difficulty, but are easily explained by early-selection models.

A dual-task investigation of automaticity in visual word processing

An analysis of activation models of visual word processing suggests that frequency-sensitive forms of lexical processing should proceed normally while unattended. This hypothesis was tested by having participants perform a speeded pitch discrimination task followed by lexical decisions or word naming. As the stimulus onset asynchrony between the tasks was reduced, lexical-decision and naming latencies increased dramatically. Word-frequency effects were additive with the increase, indicating that frequency-sensitive processing was subject to postponement while attention was devoted to the other task. Either (a) the same neural hardware shares responsibility for lexical processing and central stages of choice reaction time task processing and cannot perform both computations simultaneously, or (b) lexical processing is blocked in order to optimize performance on the pitch discrimination task. Either way, word processing is not as automatic as activation models suggest.

Visual word recognition without central attention: Evidence for greater automaticity with advancing age

The present experiments examined the automaticity of word recognition. The authors examined whether people can recognize words while central attention is devoted to another task and how this ability changes across the life span. In Experiment 1, a lexical decision Task 2 was combined with either an auditory or a visual Task 1. Regardless of the Task 1 modality, Task 2 word recognition proceeded in parallel with Task 1 central operations for older adults but not for younger adults. This is a rare example of improved cognitive processing with advancing age. When Task 2 was nonlexical (Experiment 2), however, there was no evidence for greater parallel processing for older adults. Thus, the processing advantage appears to be restricted to lexical processes. The authors conclude that greater cumulative experience with lexical processing leads to greater automaticity, allowing older adults to more efficiently perform this stage in parallel with another task.

Age differences in overlapping-task performance: Evidence for efficient parallel processing in older adults.

Two psychological refractory period (PRP) experiments were conducted to examine overlapping processing in younger and older adults. A shape discrimination task (triangle or rectangle) for Task 1 (T1) and a lexical-decision task (word or nonword) for Task 2 (T2) were used. PRP effects, response time for T2 increasing as stimulus onset synchrony (SOA) decreased, were obtained for both age groups. The effect of word frequency on T2 was smaller at the short SOA than at the long SOA, reflecting slack effects, which were larger for older than younger adults in both experiments. These results suggest that older adults can perform lexical access of T2 in parallel with the processing of T1 at least as efficiently as younger adults.

Dual-task performance with ideomotor-compatible tasks: is the central processing bottleneck intact, bypassed, or shifted in locus?

The present study examined whether the central bottleneck, assumed to be primarily responsible for the psychological refractory period (PRP) effect, is intact, bypassed, or shifted in locus with ideomotor (IM)-compatible tasks. In 4 experiments, factorial combinations of IM- and non-IM-compatible tasks were used for Task 1 and Task 2. All experiments showed substantial PRP effects, with a strong dependency between Task 1 and Task 2 response times. These findings, along with model-based simulations, indicate that the processing bottleneck was not bypassed, even with two IM-compatible tasks. Nevertheless, systematic changes in the PRP and correspondence effects across experiments suggest that IM compatibility shifted the locus of the bottleneck. The findings favor an engage-bottleneck-later hypothesis, whereby parallelism between tasks occurs deeper into the processing stream for IM- than for non-IM-compatible tasks, without the bottleneck being actually eliminated.

On the locus of dual-task interference: Is there a bottleneck at the stimulus classification stage?

Recent studies have provided evidence that dual-task interference is typically caused by a single-channel bottleneck, but the processing locus of the bottleneck has yet to be pinned down. A bottleneck locus at the response-selection stage is widely advocated, but an earlier locus would be consistent with most previous evidence. Four new experiments used the “locus of slack” method to investigate whether the stages postponed by the central bottleneck include stimulus classification, a very late stage of perceptual processing. The experiments varied stimulus classification difficulty for two different analogueue perceptual judgements. Experiment 1 found only modest absorption into slack for the difficulty of a spatial position judgement. Experiments 2–4 found virtually no absorption into slack for the difficulty of a box-width judgement. These results support a bottleneck locus beginning at or before the stage of stimulus classification and hence prior to the stage of response selection. Other evidence, however, leaves no doubt that response selection is also subject to bottleneck postponement. Two architectures are discussed that can account parsimoniously for both old and new results. One posits a single bottleneck resulting from a unified CPU-like central processor; the other posits multiple bottlenecks resulting from multiple processors accomplishing different substages of central processing.

AN EVALUATION OF THE TAXIWAY NAVIGATION AND SITUATION AWARENESS (T-NASA) SYSTEM IN HIGH-FIDELITY SIMULATION

The effects of an electronic moving map and a HUD on ground taxi performance in reduced visibility were examined in a high-fidelity simulation. Sixteen commercial flight crews completed 21 trials, each consisting of an autoland arrival to Chicago O’Hare and taxi to an apron area. Relative to a baseline (paper-chart only) condition, the EMM/HUD combination increased forward speed by 21%, and reduced navigation errors by nearly 100%. These results, together with workload ratings, situation awareness ratings, analyses of crew interactions, and pilot feedback, provide strong evidence that the combination of head-up symbology and an EMM can substantially improve both the efficiency and the safety of ground operations.

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.