Psychology

Objectives: To investigate occupational factors associated with sick leave over a 4-year period in Australian employees. Methods: Longitudinal data (self-report) from 2861 Australian full-time employees (69.4% male) were used. Occupational factors and relevant covariates were assessed at baseline with sick leave assessed yearly over a 4-year period. The data were analyzed using multinomial logistic regression models. Results: Job strain and longer commuting time were associated with long sick leave, whereas long work hours were inversely associated with long sick leave. Conclusions: These results provide further evidence that certain aspects of work are associated with sick leave, whereas other work aspects such as long work hours are inversely associated with sick leave. Organizations need to understand and address these factors to improve the well-being of employees and increase workplace productivity.

Objective: This article examined whether occupational factors predicted 4-year change in body mass index (BMI) in a sample of full-time Australian employees. Methods: Data from 1670 full-time Australian employees were collected through the Longitudinal Study of Australian Children. Multinomial logistic regression was used to examine whether several occupational factors at baseline predicted changes in BMI at 4-year follow up; several health and demographic covariates were controlled.

Memory problems are frequently associated with cannabis use, in both the short- and long-term. To date, reviews on the long-term cognitive sequelae of cannabis use have examined a broad range of cognitive functions, with none specifically focused on memory. Consequently, this review sought to examine the literature specific to memory function in cannabis users in the nontoxicated state with the aim of identifying the existence and nature of memory impairment in cannabis users and appraising potentially related mediators or moderators. Literature searches were conducted to extract well-controlled studies that investigated memory function in cannabis users outside of the acute intoxication period, with a focus on reviewing studies published within the past 10 years. Most recent studies have examined working memory and verbal episodic memory and cumulatively, the evidence suggests impaired encoding, storage, manipulation and retrieval mechanisms in long-term or heavy cannabis users. These impairments are not dissimilar to those associated with acute intoxication and have been related to the duration, frequency, dose and age of onset of cannabis use. We consider the impact of not only specific parameters of cannabis use in the manifestation of memory dysfunction, but also such factors as age, neurodevelopmental stage, IQ, gender, various vulnerabilities and other substance-use interactions, in the context of neural efficiency and compensatory mechanisms. The precise nature of memory deficits in cannabis users, their neural substrates and manifestation requires much further exploration through a variety of behavioural, functional brain imaging, prospective and genetic studies.

We examined the eye movements of pilots as they carried out simulated aircraft landings under day and night lighting conditions. Our five students and five certified pilots were instructed to quickly achieve and then maintain a constant 3-degree glideslope relative to the runway. However, both groups of pilots were found to make significant glideslope control errors, especially during simulated night approaches. We found that pilot gaze was directed most often toward the runway and to the ground region located immediately in front of the runway, compared to other visual scene features. In general, their gaze was skewed toward the near half of the runway and tended to follow the runway threshold as it moved on the screen. Contrary to expectations, pilot gaze was not consistently directed at the aircraft's simulated aimpoint (i.e., its predicted future touchdown point based on scene motion). However, pilots did tend to fly the aircraft so that this point was aligned with the runway threshold. We conclude that the supplementary out-of-cockpit visual cues available during day landing conditions facilitated glideslope control performance. The available evidence suggests that these supplementary visual cues are acquired through peripheral vision, without the need for active fixation.

This study examined vection induced during physical or simulated head oscillation along either the horizontal or depth axis. In the first two experiments, during active conditions, subjects' viewed radial flow displays which simulated viewpoint oscillation that was either in-phase or out-of-phase with their own tracked head movements. In passive conditions, stationary subjects viewed playbacks of displays generated in earlier active conditions. A third control experiment was also conducted where physical and simulated fore-aft oscillation was added to a lamellar flow display. Consistent with ecology, when active in-phase horizontal oscillation was added to a radial flow display it modestly improved vection compared to active outof-phase and passive conditions. However, when active fore-aft head movements were added to either a radial or a lamellar flow display, both in-phase and out-ofphase conditions produced very similar vection. Our research shows that consistent multisensory input can enhance the visual perception of self-motion in some situations. However, it is clear that multisensory stimulation does not have to be consistent (i.e. ecological) to generate compelling vection in depth.

We examined the vection induced by consistent and conflicting multisensory information about self--motion. Observers viewed displays simulating constant velocity self--motion in depth while physically oscillating their heads left--right or back--forth (in time with a metronome). Their tracked head movements were either ignored or incorporated directly into the self--motion display (as an added simulated self-acceleration). When this head oscillation was updated into displays, sensory conflict was generated by simulating oscillation along: (i) an orthogonal--axis to the head movement; or (ii) the same--axis, but in a non--ecological direction. Simulated head oscillation always produced stronger vection than 'no display oscillation' -even when the axis/direction of this display motion was inconsistent with the physical head motion. When head--and--display oscillation occurred along the same axis: (i) consistent (in--phase) horizontal display oscillation produced stronger vection than conflicting (out--of--phase) horizontal display oscillation; however (ii) consistent and conflicting depth oscillation conditions did not induce significantly different vection. Overall, orthogonal--axis oscillation was found to produce very similar vection to same--axis oscillation. Thus, we conclude that while vection appears to be very robust to sensory conflict, there are situations where sensory consistency improves vection.

Vection has typically been induced in stationary observers (i.e. conditions providing visual--only information about self--motion). Two recent studies have examined vection during active treadmill walking -one reported that treadmill walking in the same direction as the visually simulated self--motion impaired vection (Onimaru et al. 2010), the other reported that it enhanced vection (Seno et al. 2011). Our study expands on these earlier investigations of vection during observer active movement. In Experiment 1, we presented radially expanding optic flow and compared the vection produced in stationary observers to that produced during walking forward on a treadmill at a 'matched' speed.

The utility of P50 paired-click measures is limited by their unestablished reliability, unknown effects of time, and long protocol. This study measured within-session reliability, temporal course, effect of varying interpair interval (IPI), and peak definition and ratio calculation methods on P50 paired-click measures in healthy participants. Results indicate higher reliability for difference (ICC=.72) than ratio (ICC=.44) method; when P50 peaks are defined as baseline-to-peak than peak-to-peak; time-related changes; and comparable P50 paired-click measures at long (9 s) and short (3–7 s) IPIs. After controlling for time effects, P50 paired-click measures are relatively reliable within-session and are best measured using the difference method and defined as baseline-to-peak amplitude; time effects must be taken into account when measuring P50 paired-click measures in a long paradigm; and IPI can be shortened in studies with healthy samples.

Prolonged exposure to cannabis is associated with impairments in sensory gating.Long-term users exhibit poor sensory gating compared to controls and short-term users.P50 deficits are associated with schizophrenia, and may indicate a similar pathology.Chronic cannabis use has been associated with neurocognitive deficits, alterations in brain structure and function, and with psychosis. This study investigated the effects of chronic cannabis use on P50 sensory-gating in regular users, and explored the association between sensory gating, cannabis use history and the development of psychotic-like symptoms. Twenty controls and 21 regular cannabis users completed a P50 paired-click (S1 and S2) paradigm with an inter-pair interval of 9 s. The groups were compared on P50 amplitude to S1 and S2, P50 ratio (S2/S1) and P50 difference score (S1–S2). While cannabis users overall did not differ from controls on P50 measures, prolonged duration of regular use was associated with greater impairment in sensory gating as indexed by both P50 ratio and difference scores (including after controlling for tobacco use). Long-term cannabis users were found to have worse sensory gating ratios and difference scores compared to short-term users and controls. P50 metrics did not correlate significantly with any measure of psychotic-like symptoms in cannabis users. These results suggest that prolonged exposure to cannabis results in impaired P50 sensory-gating in long-term cannabis users. While it is possible that these deficits may have pre-dated cannabis use and reflect a vulnerability to cannabis use, their association with increasing years of cannabis use suggests that this is not the case. Impaired P50 sensory-gating ratios have also been reported in patients with schizophrenia and may indicate a similar underlying pathology.

We studied binocular rivalry between orthogonally translating arrays of random Gaussian blobs and measured the strength of rivalry suppression for static oriented probes. Suppression depth was quantified by expressing monocular probe thresholds during dominance relative to thresholds during suppression. Rivalry between two fast motions or two slow motions was compared in order to test the suggestion that fast-moving objects leave oriented “motion streaks” due to temporal integration (W. S. Geisler, 1999). If fast motions do produce motion streaks, then fast motion rivalry might also entail rivalry between the orthogonal streak orientations. We tested this using a static oriented probe that was aligned either parallel to the motion trajectory (hence collinear with the “streaks”) or was orthogonal to the trajectory, predicting that rivalry suppression would be greater for parallel probes, and only for rivalry between fast motions. Results confirmed that suppression depth did depend on probe orientation for fast motion but not for slow motion. Further experiments showed that threshold elevations for the oriented probe during suppression exhibited clear orientation tuning. However, orientation-tuned elevations were also present during dominance, suggesting within-channel masking as the basis of the extra-deep suppression. In sum, the presence of orientation-dependent suppression in fast motion rivalry is consistent with the “motion streaks” hypothesis.

Fast-moving visual features are thought to leave neural ‘streaks’ that can be detected by orientation-selective cells. Here, we tested whether ‘motion streaks’ can induce classic tilt aftereffects (TAEs) and tilt illusions (TIs). For TAEs, participants adapted to random arrays of small Gaussian blobs drifting at 9.5 deg/s. Following adaptation to directions of 15, 30, 45, 60, 75, and 90 degrees (clockwise from vertical) subjective vertical was measured for a briefly presented test grating. For TIs, the same motions were presented in an annular surround and subjective vertical was measured for a simultaneously presented central grating. All motions were 50% coherent, with half the blobs following random-walk paths and half following a fixed direction. Strong and weak streaks were compared by varying streak length (the number of fixed-walk frames), rather than by manipulating speed, so that speed and coherence were matched in all conditions. Strong motion streaks produced robust TAEs and TIs, similar in magnitude and orientation tuning to those induced by tilted lines. These effects were weak or absent in weak streak conditions, and when motion was too slow to form streaks. Together, these results indicate that motion streaks produced by temporal integration of fast translating features do effectively adapt orientation-selective cells and may therefore be exploited to improve perception of motion direction as described in the ‘motion streaks’ model.

We investigated whether the oriented trails of blur left by fast-moving dots (i.e., “motion streaks”) effectively mask grating targets. Using a classic overlay masking paradigm, we varied mask contrast and target orientation to reveal underlying tuning. Fast-moving Gaussian blob arrays elevated thresholds for detection of static gratings, both monoptically and dichoptically. Monoptic masking at high mask (i.e., streak) contrasts is tuned for orientation and exhibits a similar bandwidth to masking functions obtained with grating stimuli (~30 degrees). Dichoptic masking fails to show reliable orientation-tuned masking, but dichoptic masks at very low contrast produce a narrowly tuned facilitation (`17 degrees). For iso-oriented streak masks and grating targets, we also explored masking as a function of mask contrast. Interestingly, dichoptic masking shows a classic “dipper”-like TVC function, whereas monoptic masking shows no dip and a steeper “handle”. There is a very strong unoriented component to the masking, which we attribute to transiently biased temporal frequency masking. Fourier analysis of “motion streak” images shows interesting differences between dichoptic and monoptic functions and the information in the stimulus. Our data add weight to the growing body of evidence that the oriented blur of motion streaks contributes to the processing of fast motion signals.

Although visual systems are optimized to deal with the natural visual environment, our understanding of human motion perception is in large part based on the use of artificial stimuli. Here, we assessed observers' ability to estimate the direction of translating natural images and fractals by having them adjust the orientation of a subsequently viewed line. A system of interleaved staircases, driven by observers' direction estimates, ensured that stimuli were presented near one of 16 reference directions. The resulting error distributions (i.e., the differences between reported and true directions) reveal several anisotropies in global motion processing. First, observers' estimates are biased away from cardinal directions (reference repulsion). Second, the standard deviations of estimates show an “oblique effect” being ∼45% lower around cardinal directions. Third, errors around cardinal directions are more likely (∼22%) to approach zero than would be consistent with Gaussian-distributed errors, suggesting that motion processing minimizes the number as well as magnitude of errors. Fourth, errors are similar for natural scenes and fractals, indicating that observers do not use top-down information to improve performance. Finally, adaptation to unidirectional motion modifies observers' bias by amplifying existing repulsion (e.g., around cardinal directions). This bias change can improve direction discrimination but is not due to a reduction in variability.