A review of the perceptual and cognitive issues associated with the use of head-up displays in commercial aviation

A head-up display (HUD) is a projection of symbology into the pilot's forward field of view that enables the pilot to monitor the instrumentation while, theoretically, also viewing the external domain. Although the HUD has been shown to improve flight performance, there are perceptual and cognitive issues that need to be addressed. This article reviews selected literature that investigates these issues and the possible solutions posed and identifies areas that remain in doubt.

An analysis of relational complexity in an air traffic control conflict detection task

Theoretical analyses of air traffic complexity were carried out using the Method for the Analysis of Relational Complexity. Twenty-two air traffic controllers examined static air traffic displays and were required to detect and resolve conflicts. Objective measures of performance included conflict detection time and accuracy. Subjective perceptions of mental workload were assessed by a complexity-sorting task and subjective ratings of the difficulty of different aspects of the task. A metric quantifying the complexity of pair-wise relations among aircraft was able to account for a substantial portion of the variance in the perceived complexity and difficulty of conflict detection problems, as well as reaction time. Other variables that influenced performance included the mean minimum separation between aircraft pairs and the amount of time that aircraft spent in conflict.

Telling the story of theory of mind: Deaf and hearing children's narratives and mental state understanding

Theory of mind (ToM) was examined in late-signing deaf children in two studies by using standard tests and measures of spontaneous talk about inner states of perception, affect and cognition during storytelling. In Study 1, there were 21 deaf children aged 6 to 11 years and 13 typical-hearing children matched with the deaf by chronological age. In Study 2, there were 17 deaf children aged 6 to 12 years and 17 typical-hearing preschoolers aged 4 to 5 years who were matched with the deaf by ToM test performance. In addition to replicating the consistently reported finding of poor performance on standard false belief tests by late-signing deaf children, significant correlations emerged in both studies between deaf children's ToM test scores and their spontaneous narrative talk about imaginative cognition (e.g. 'pretend'). In Study 2, with a new set of purpose-built pictures that evoked richer and more complex mentalistic narration than the published picture book of Study 1, results of multiple regression analyses showed that children's narrative talk about imaginative cognition was uniquely important, over and above hearing status and talking of other kinds of mental states, in predicting ToM scores. The same was true of children's elaborated narrative talk using utterances that either spelt out thoughts, explained inner states or introduced contrastives. In addition, results of a Guttman scalograrn analysis in Study 2 suggested a consistent sequence in narrative and standard test performance by deaf and hearing children that went from (1) narrative mention of visible (affective or perceptual) mental states only, along with FB failure, to (2) narrative mention of cognitive states along with (1), to (3) elaborated narrative talk about inner states along with (2), and finally to (4) simple and elaborated narrative talk about affective/perceptual and cognitive states along with FIB test success. Possible explanations for this performance ordering, as well as for the observed correlations in both studies between ToM test scores and narrative variables, were considered.

Spatially localized distortions of event time

A fundamental question about the perception of time is whether the neural mechanisms underlying temporal judgements are universal and centralized in the brain or modality specific and distributed []. Time perception has traditionally been thought to be entirely dissociated from spatial vision. Here we show that the apparent duration of a dynamic stimulus can be manipulated in a local region of visual space by adapting to oscillatory motion or flicker. This implicates spatially localized temporal mechanisms in duration perception. We do not see concomitant changes in the time of onset or offset of the test patterns, demonstrating a direct local effect on duration perception rather than an indirect effect on the time course of neural processing. The effects of adaptation on duration perception can also be dissociated from motion or flicker perception per se. Although 20 Hz adaptation reduces both the apparent temporal frequency and duration of a 10 Hz test stimulus, 5 Hz adaptation increases apparent temporal frequency but has little effect on duration perception. We conclude that there is a peripheral, spatially localized, essentially visual component involved in sensing the duration of visual events.

Reflexive OKN with partial and full field stimulation: Effects of age and light level

We recorded reflexive OKN in ten younger (32.3±5.98 years) and older (65.6±6.53) visually normal subjects under viewing conditions designed to differentiate M-pathway functioning from other pathways. Subjects were required to gaze straight ahead while viewing vertical gratings of either 0.43 or 1.08 cpd, drifting at either 5 or 20°/sec and presented at either 8 or 80% contrast. Gratings were presented as full field stimulation, central stimulation or peripheral (>15°) stimulation. The order of presentation of conditions was pseudo-randomised at two blocked light levels: ‘mesopic’ or twilight conditions (1.8 cdm-2) and ‘photopic’ or full light conditions (71.5 cdm-2). For the partial fields, central stimulation, mesopic light level, lower temporal frequencies (i.e. number of stripes passing per second) each contributed to greater OKN strength as measured by slow-phase velocity (SPV). For full field stimulation, and especially for higher temporal frequencies and low contrast, there was a significant interaction between age group × light level (p = 0.017): SPV diminished much more among the older than the younger group for the twilight condition compared to full light. Such a clear diminution in M-pathway sensitivity revealed by OKN response has important implications for everyday situations like crash avoidance under twilight driving conditions.

The effect of reduced contrast on drivers' speed perception

It has been demonstrated, using abstract psychophysical stimuli, that speeds appear slower when contrast is reduced under certain conditions. Does this effect have any real life consequences? One previous study has found, using a low fidelity driving simulator, that participants perceived vehicle speeds to be slower in foggy conditions. We replicated this finding with a more realistic video-based simulator using the Method of Constant Stimuli. We also found that lowering contrast reduced participants’ ability to discriminate speeds. We argue that these reduced contrast effects could partly explain the higher crash rate of drivers with cataracts (this is a substantial societal problem and the crash relationship variance can be accounted for by reduced contrast). Note that even if people with cataracts can calibrate for the shift in their perception of speed using their speedometers (given that cataracts are experienced over long periods), they may still have an increased chance of making errors in speed estimation due to poor speed discrimination. This could result in individuals misjudging vehicle trajectories and thereby inflating their crash risk. We propose interventions that may help address this problem.

Signal detection theory in applied tasks: The case of hazard perception in driving

Fuzzy signal detection analysis can be a useful complementary technique to traditional signal detection theory analysis methods, particularly in applied settings. For example, traffic situations are better conceived as being on a continuum from no potential for hazard to high potential, rather than either having potential or not having potential. This study examined the relative contribution of sensitivity and response bias to explaining differences in the hazard perception performance of novices and experienced drivers, and the effect of a training manipulation. Novice drivers and experienced drivers were compared (N = 64). Half the novices received training, while the experienced drivers and half the novices remained untrained. Participants completed a hazard perception test and rated potential for hazard in occluded scenes. The response latency of participants to the hazard perception test replicated previous findings of experienced/novice differences and trained/untrained differences. Fuzzy signal detection analysis of both the hazard perception task and the occluded rating task suggested that response bias may be more central to hazard perception test performance than sensitivity, with trained and experienced drivers responding faster and with a more liberal bias than untrained novices. Implications for driver training and the hazard perception test are discussed.