Five state factors control progressive stages of freshwater salinization syndrome.

Factors driving freshwater salinization syndrome (FSS) influence the severity of impacts and chances for recovery. We hypothesize that spread of FSS across ecosystems is a function of interactions among five state factors: human activities, geology, flowpaths, climate, and time. (1) Human activities drive pulsed or chronic inputs of salt ions and mobilization of chemical contaminants. (2) Geology drives rates of erosion, weathering, ion exchange, and acidification-alkalinization. (3) Flowpaths drive salinization and contaminant mobilization along hydrologic cycles. (4) Climate drives rising water temperatures, salt stress, and evaporative concentration of ions and saltwater intrusion. (5) Time influences consequences, thresholds, and potentials for ecosystem recovery. We hypothesize that state factors advance FSS in distinct stages, which eventually contribute to failures in systems-level functions (supporting drinking water, crops, biodiversity, infrastructure, etc.). We present future research directions for protecting freshwaters at risk based on five state factors and stages from diagnosis to prognosis to cure.

Sensitivity to auditory-tactile colocation in early infancy.

An ability to detect the common location of multisensory stimulation is essential for us to perceive a coherent environment, to represent the interface between the body and the external world, and to act on sensory information. Regarding the tactile environment "at hand", we need to represent somatosensory stimuli impinging on the skin surface in the same spatial reference frame as distal stimuli, such as those transduced by vision and audition. Across two experiments we investigated whether 6- (n = 14; Experiment 1) and 4-month-old (n = 14; Experiment 2) infants were sensitive to the colocation of tactile and auditory signals delivered to the hands. We recorded infants' visual preferences for spatially congruent and incongruent auditory-tactile events delivered to their hands. At 6 months, infants looked longer toward incongruent stimuli, whilst at 4 months infants looked longer toward congruent stimuli. Thus, even from 4 months of age, infants are sensitive to the colocation of simultaneously presented auditory and tactile stimuli. We conclude that 4- and 6-month-old infants can represent auditory and tactile stimuli in a common spatial frame of reference. We explain the age-wise shift in infants' preferences from congruent to incongruent in terms of an increased preference for novel crossmodal spatial relations based on the accumulation of experience. A comparison of looking preferences across the congruent and incongruent conditions with a unisensory control condition indicates that the ability to perceive auditory-tactile colocation is based on a crossmodal rather than a supramodal spatial code by 6 months of age at least.

Warning Drivers about Impending Collisions Using Vibrotactile Flow.

Vibrotactile collision warning signals that create a sensation of motion across a driver's body result in faster brake reaction times (BRTs) to potential collision events. To date, however, such warnings have only simulated linear motion. We extended this research by exploring the effectiveness of collision warnings that incorporate vibrotactile patterns or "vibrotactile flow". In Experiment 1, expanding and contracting vibrotactile flow warnings were compared with a static warning (all tactors activated simultaneously) and a no warning condition in a car following scenario. Both vibrotactile flow warnings produced significantly faster BRTs than the static and no warning conditions. However, there was no directional effect. That is, there was no significant difference between contracting and expanding signals. Warnings that utilize vibrotactile flow therefore appear to provide an effective means of informing drivers about potential collision events. However, unlike comparable warnings utilizing linear motion, their effectiveness does not seem to depend on the precise relationship between the warning and collision events. Experiment 2 demonstrated that a tactile warning incorporating linear motion produced significantly faster BRTs than an expanding vibrotactile flow warning. Taken together, these results suggest that vibrotactile warnings that simulate linear motion may be more effective than vibrotactile flow warnings.

Dynamic vibrotactile signals for forward collision avoidance warning systems.

OBJECTIVE: Four experiments were conducted in order to assess the effectiveness of dynamic vibrotactile collision-warning signals in potentially enhancing safe driving. BACKGROUND: Auditory neuroscience research has demonstrated that auditory signals that move toward a person are more salient than those that move away. If this looming effect were found to extend to the tactile modality, then it could be utilized in the context of in-car warning signal design. METHOD: The effectiveness of various vibrotactile warning signals was assessed using a simulated car-following task. The vibrotactile warning signals consisted of dynamic toward-/away-from-torso cues (Experiment 1), dynamic versus static vibrotactile cues (Experiment 2), looming-intensity- and constant-intensity-toward-torso cues (Experiment 3), and static cues presented on the hands or on the waist, having either a low or high vibration intensity (Experiment 4). RESULTS: Braking reaction times (BRTs) were significantly faster for toward-torso as compared to away-from-torso cues (Experiments 1 and 2) and static cues (Experiment 2). This difference could not have been attributed to differential responses to signals delivered to different body parts (i.e., the waist vs. hands; Experiment 4). Embedding a looming-intensity signal into the toward-torso signal did not result in any additional BRT benefits (Experiment 3). CONCLUSION: Dynamic vibrotactile cues that feel as though they are approaching the torso can be used to communicate information concerning external events, resulting in a significantly faster reaction time to potential collisions. APPLICATION: Dynamic vibrotactile warning signals that move toward the body offer great potential for the design of future in-car collision-warning system.

Dynamic vibrotactile warning signals for frontal collision avoidance: towards the torso versus towards the head.

Three experiments were conducted to assess the effectiveness of dynamic vibrotactile warning signals with different spatial patterns and to compare dynamic towards-torso and towards-head vibrotactile warnings in a simulated driving task. The results revealed that embedding additional stimuli between the participant's hands and waist in the towards-torso cues (Experiment 1) and increasing the spatial distance between adjacent stimuli in the towards-head cues (Experiment 2) did not result in any further benefits in braking response times (BRTs). The triple towards-head cues resulting from the sequential operation of three pairs of stimuli on the torso gave rise to a significant advantage over the static cues; however, it did not outperform the dynamic towards-torso cues with just two pairs of stimuli. Taken together, these results demonstrated the promise of dynamic vibrotactile warnings (especially, the towards-torso warnings) in terms of the future design of more effective rear-end collision warnings. PRACTITIONER SUMMARY: Three experiments assessed the effectiveness of dynamic towards-torso and towards-head vibrotactile warning signals in a simulated driving task. The results demonstrated the promise of dynamic vibrotactile warnings (especially, the towards-torso vibrotactile warnings) in terms of the future design of more effective frontal collision warnings.

Effectively responding to tactile stimulation: do homologous cue and effector locations really matter?

We report a study designed to investigate the extent to which speeded behavioral responses following tactile stimulation are influenced by differences in neural conduction latencies at different body sites and/or by the characteristics of the compatibility between the cue and effector. The results showed that it may not be particularly desirable to present tactile cues (e.g., warning signals) to an interface operator's feet if a speeded foot response is required, for even though such an arrangement maximizes the set-level compatibility between the stimulus and the response, it turns out that response latencies are primarily determined by conduction latencies through the peripheral nervous system.

Reorienting driver attention with dynamic tactile cues.

A series of three experiments was designed to investigate whether the presentation of moving tactile warning signals that are presented in a particular spatiotemporal configuration may be particularly effective in terms of facilitating a driver's response to a target event. In the experiments reported here, participants' visual attention was manipulated such that they were either attending to the frontal object that might occasionally approach them on a collision course, or else they were distracted by a color discrimination task presented from behind. We measured how rapidly participants were able to initiate a braking response to a looming visual target following the onset of vibrotactile warning signals presented from around their waist. The vibrotactile warning signals consisted of single, double, and triple upward moving cues (Experiment 1), triple upward and downward moving cues (Experiment 2), and triple random cues (Experiment 3). The results demonstrated a significant performance advantage following the presentation of dynamic triple cues over the static single tactile cues, regardless of the specific configuration of the triple cues. These findings point to the potential benefits of embedding dynamic information in warning signals for dynamic target events. These findings have important implications for the design of future vibrotactile warning signals.

A comparison of different informative vibrotactile forward collision warnings: does the warning need to be linked to the collision event?

Recent research demonstrates that auditory and vibrotactile forward collision warnings presenting a motion signal (e.g., looming or apparent motion across the body surface) can facilitate speeded braking reaction times (BRTs). The purpose of the present study was to expand on this work by directly comparing warning signals in which the motion conveyed was constant across all collision events with signals in which the speed of motion was dependent on the closing velocity (CV). Two experiments were conducted using a simulated car-following task and BRTs were measured. In Experiment 1, increasing intensity (looming) vibrotactile signals were presented from a single tactor attached to the driver's waist. When the increase in intensity was CV-linked, BRTs were significantly faster as compared to a no-warning condition, however, they were not significantly different from constant intensity and CV-independent looming warnings. In Experiment 2, a vertical array of three tactors was used to create motion either towards (upwards) or away (downwards) from the driver's head. When the warning signal presented upwards motion that was CV-linked, BRTs were significantly faster than all other warning types. Downwards warnings led to a significantly higher number of brake activations in false alarm situations as compared to upwards moving warnings. The effectiveness of dynamic tactile collision warnings would therefore appear to depend on both the link between the warning and collision event and on the directionality of the warning signal.

Assessing the benefits of multisensory audiotactile stimulation for overweight individuals.

We report an experiment designed to examine whether individuals who are overweight would perform differently when trying to detect and/or discriminate auditory, vibrotactile, and audiotactile targets. The vibrotactile stimuli were delivered either to the participant's abdomen or to his hand. Thirty-six young male participants were classified into normal, underweight, or overweight groups based on their body mass index. All three groups exhibited a significant benefit of multisensory (over the best of the unisensory) stimulation, but the magnitude of this benefit was modulated by the weight of the participant, the task, and the location from which the vibrotactile stimuli happened to be presented. For the detection task, the overweight group exhibited a significantly smaller benefit than the underweight group. In the discrimination task, the overweight group showed significantly more benefits than the other two groups when the vibrotactile stimuli were delivered to their hands, but not when the stimuli were delivered to their abdomens. These results might raise some interesting questions regarding the mechanisms underlying audiotactile information processing and have applied relevance for the design of the most effective warning signal (e.g., for drivers).

Role of audiovisual synchrony in driving head orienting responses.

Many studies now suggest that optimal multisensory integration sometimes occurs under conditions where auditory and visual stimuli are presented asynchronously (i.e. at asynchronies of 100 ms or more). Such observations lead to the suggestion that participants' speeded orienting responses might be enhanced following the presentation of asynchronous (as compared to synchronous) peripheral audiovisual spatial cues. Here, we report a series of three experiments designed to investigate this issue. Upon establishing the effectiveness of bimodal cuing over the best of its unimodal components (Experiment 1), participants had to make speeded head-turning or steering (wheel-turning) responses toward the cued direction (Experiment 2), or an incompatible response away from the cue (Experiment 3), in response to random peripheral audiovisual stimuli presented at stimulus onset asynchronies ranging from -100 to 100 ms. Race model inequality analysis of the results (Experiment 1) revealed different mechanisms underlying the observed multisensory facilitation of participants' head-turning versus steering responses. In Experiments 2 and 3, the synchronous presentation of the component auditory and visual cues gave rise to the largest facilitation of participants' response latencies. Intriguingly, when the participants had to subjectively judge the simultaneity of the audiovisual stimuli, the point of subjective simultaneity occurred when the auditory stimulus lagged behind the visual stimulus by 22 ms. Taken together, these results appear to suggest that the maximally beneficial behavioural (head and manual) orienting responses resulting from peripherally presented audiovisual stimuli occur when the component signals are presented in synchrony. These findings suggest that while the brain uses precise temporal synchrony in order to control its orienting responses, the system that the human brain uses to consciously judge synchrony appears to be less fine tuned.

Crowding by invisible flankers.

BACKGROUND: Human object recognition degrades sharply as the target object moves from central vision into peripheral vision. In particular, one's ability to recognize a peripheral target is severely impaired by the presence of flanking objects, a phenomenon known as visual crowding. Recent studies on how visual awareness of flanker existence influences crowding had shown mixed results. More importantly, it is not known whether conscious awareness of the existence of both the target and flankers are necessary for crowding to occur. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that crowding persists even when people are completely unaware of the flankers, which are rendered invisible through the continuous flash suppression technique. Contrast threshold for identifying the orientation of a grating pattern was elevated in the flanked condition, even when the subjects reported that they were unaware of the perceptually suppressed flankers. Moreover, we find that orientation-specific adaptation is attenuated by flankers even when both the target and flankers are invisible. CONCLUSIONS: These findings complement the suggested correlation between crowding and visual awareness. What's more, our results demonstrate that conscious awareness and attention are not prerequisite for crowding.

Using peripersonal warning signals to orient a driver's gaze.

OBJECTIVE: We report a series of three experiments designed to assess the relative speed with which people can initiate speeded head-orienting responses following the presentation of spatial warning signals. BACKGROUND: Recent cognitive neuroscience findings have shown that the human brain tends to treat stimuli occurring in peripersonal space as being somehow more behaviorally relevant and attention demanding than stimuli occurring in extrapersonal space. These brain mechanisms may be exploited in the design of warning signals. METHOD: Experiment 1 assessed the effectiveness of various different unisensory warning signals in eliciting a head-turning response to look at the potential source of danger requiring participants' immediate attention; Experiment 2 assessed the latency of a driver's responses to events occurring in the cued direction; Experiment 3 assessed the relative effectiveness of various warning signals in reorienting a person's gaze back to a central driving task while he or she was distracted by a secondary task. RESULTS: The results show that participants initiated head-turning movements and made speeded discrimination or braking responses significantly more rapidly following the presentation of a close rear auditory warning signal than following the presentation of either a far frontal auditory warning signal, a vibrotactile warning signal presented to their waist, or a peripheral visual warning signal. CONCLUSION: These results support the claim that the introduction of peripersonal warning signals results in a significant performance advantage relative to traditionally designed warnings. APPLICATION: Warning systems that have been designed around the constraints of the human brain offer great potential in the future design ofmultisensory interfaces.

Multisensory warning signals: when spatial correspondence matters.

We report a study designed to investigate the effectiveness of task-irrelevant unimodal and bimodal audiotactile stimuli in capturing a person's spatial attention away from a highly perceptually demanding central rapid serial visual presentation (RSVP) task. In "Experiment 1", participants made speeded elevation discrimination responses to peripheral visual targets following the presentation of auditory stimuli that were either presented alone or else were paired with centrally presented tactile stimuli. The results showed that the unimodal auditory stimuli only captured spatial attention when participants were not performing the RSVP task, while the bimodal audiotactile stimuli did not result in any performance change in any of the conditions. In "Experiment 2", spatial auditory stimuli were either presented alone or else were paired with a tactile stimulus presented from the same direction. In contrast to the results of "Experiment 1", the bimodal audiotactile stimuli were especially effective in capturing participants' spatial attention from the concurrent RSVP task. These results therefore provide support for the claim that auditory and tactile stimuli should be presented from the same direction if they are to capture attention effectively. Implications for multisensory warning signal design are discussed.

Capturing spatial attention with multisensory cues.

We assessed the influence ofmultisensory interactions on the exogenous orienting of spatial attention by comparing the ability of auditory, tactile, and audiotactile exogenous cues to capture visuospatial attention under conditions of no perceptual load versus high perceptual load. In Experiment 1, participants discriminated the elevation of visual targets preceded by either unimodal or bimodal cues under conditions of either a high perceptual load (involving the monitoring of a rapidly presented central stream of visual letters for occasionally presented target digits) or no perceptual load (when the central stream was replaced by a fixation point). All of the cues captured spatial attention in the no-load condition, whereas only the bimodal cues captured visuospatial attention in the high-load condition. In Experiment 2, we ruled out the possibility that the presentation of any changing stimulus at fixation (i.e., a passively monitored stream of letters) would eliminate exogenous orienting, which instead appears to be a consequence of high perceptual load conditions (Experiment 1). These results demonstrate that multisensory cues capture spatial attention more effectively than unimodal cues under conditions of concurrent perceptual load.

Multisensory in-car warning signals for collision avoidance.

OBJECTIVE: A driving simulator study was conducted in order to assess the relative utility of unimodal auditory, unimodal vibrotactile, and combined audiotactile (i.e., multisensory) in-car warning signals to alert and inform drivers of likely front-to-rear-end collision events in a situation modeled on real-world driving. BACKGROUND: The implementation of nonvisual in-car warning signals may have important safety implications in lessening any visual overload during driving. Multisensory integration can provide synergistic facilitation effects. METHOD: The participants drove along a rural road in a car-following scenario in either the presence or absence of a radio program in the background. The brake light signals of the lead vehicle were also unpredictably either enabled or disabled on a trial-by-trial basis. RESULTS: The results showed that the participants initiated their braking responses significantly more rapidly following the presentation of audiotactile warning signals than following the presentation of either unimodal auditory or unimodal vibrotactile warning signals. CONCLUSION: Multisensory warning signals offer a particularly effective means of capturing driver attention in demanding situations such as driving. APPLICATION: The potential value of such multisensory in-car warning signals is explained with reference to recent cognitive neuroscience research.

Head orientation biases tactile localization.

Does the perceived location of tactile stimuli presented on the torso depend on the orientation of our heads with respect to our bodies? An experiment is reported that was designed to assess whether the subjective perception of tactile stimuli on the torso changes as people turn their heads in different directions. Our participants used a scale presented on a computer monitor to indicate the perceived position of vibrotactile stimuli presented to one of eight different positions around the frontal side of their waist while they either looked straight ahead, turned their head to the left, or else turned their head to the right. The results showed that the perceived location of tactile stimuli was systematically influenced by head orientation. In particular, the perceived location of the tactile stimuli shifted away from their actual position in the direction opposite to the direction of the participant's head turn. Our results also revealed a systematic decline in the accuracy of tactile localization as a function of the physical distance of the tactile stimuli from the participant's navel. These results echo related findings in the auditory domain where it has been shown that changes in eye position affect auditory lateralization. Our results also have important implications for the design of tactile displays for presenting directional information in a variety of real-world applications.

An investigation into the temporal dimension of the Mozart effect: evidence from the attentional blink task.

In the present study, we examined whether the 'Mozart effect' would influence participants' temporal attention using a visual attentional blink (AB) task that provides a reliable measure of the temporal dynamics of visual attention. The 'Mozart effect' refers to the specific claim that listening to Mozart's Sonata for Two Pianos in D Major, K.448 can improve the performance in spatio-temporal tasks. Participants had to try and identify two target digits (in their correct order of presentation) presented amongst a stream of distractor letters in three different conditions (presented in separate blocks of trials): while listening to the Mozart sonata played normally, while listening to the same Mozart sonata played in reverse, and while in silence. The results showed that the participants were able to detect the second target (T2) significantly more accurately (given the correct detection of the first target, T1) in the AB stream when the Mozart sonata was played normally than in either of the other two conditions. Possible explanations for the differential effects of Mozart's music being played normally and in reverse and potential confounds in previous studies reporting a facilitatory 'Mozart effect' are discussed. Our results therefore provide the first empirical demonstration supporting the existence of a purely temporal component to the 'Mozart effect' using a non-spatial visual AB task.

Assessing the effectiveness of "intuitive" vibrotactile warning signals in preventing front-to-rear-end collisions in a driving simulator.

This study was designed to investigate the possibility that driver responses to potential front-to-rear-end collision situations could be facilitated by implementing vibrotactile warning signals that indicate the likely direction of the potential collision. In a car following scenario in a driving simulator, participants drove along a rural road while trying to maintain a safe headway distance to the lead car using a visual distance display. Participants had to respond as quickly as possible to the sudden deceleration of the lead car which had its brake lights disabled, either with or without vibrotactile cues (presented in different experimental blocks). The results demonstrated significantly faster braking responses and larger safety margins when the vibrotactile warning signal was presented than when it was not. These findings demonstrate the effectiveness of vibrotactile cues in helping drivers to orient their spatial attention in the appropriate direction. Our results add to a growing body of empirical evidence highlighting the potential benefits of using "intuitive" vibrotactile in-car displays, in this case, to alert drivers to potential collisions and to provide time-critical directional information.

The differential effect of vibrotactile and auditory cues on visual spatial attention.

Previous research has shown that the presentation of spatially predictive auditory and vibrotactile warning signals can facilitate driver responses to driving events seen through the windscreen or rearview mirror. The present study investigated whether this facilitation reflects the priming of the appropriate response (i.e. braking vs. accelerating) or an attentional cuing effect (i.e. a perceptual benefit that facilitates subsequent behavioural responding). In the experiments reported here, participants had to discriminate the colour of a number plate (red vs. blue) following the presentation of either spatially predictive vibrotactile (experiment 1) or auditory (experiment 2) warning signals that indicated the likely location (front or back) of the visual target, while simultaneously performing a highly attention-demanding rapid serial visual presentation task. Numberplate discrimination performance was facilitated following the presentation of valid auditory cues, but not following the presentation of equally informative vibrotactile cues. The use of an orthogonal spatial cuing design enabled with us to rule out of a potential response priming account of these data. The results suggest that whilst directional congruency between a warning signal and a target event may be sufficient to facilitate performance due to the priming of the appropriate response, attentional facilitation effects may also require the co-location of the cue and target within the same functional region of space.

Assessing the effectiveness of various auditory cues in capturing a driver's visual attention.

This study was designed to assess the potential benefits of using spatial auditory warning signals in a simulated driving task. In particular, the authors assessed the possible facilitation of responses (braking or accelerating) to potential emergency driving situations (the rapid approach of a car from the front or from behind) seen through the windshield or the rearview mirror. Across 5 experiments, the authors assessed the efficacy of nonspatial-nonpredictive (neutral), spatially nonpredictive (50% valid), and spatially predictive (80% valid) car horn sounds, as well as symbolic predictive and spatially presented symbolic predictive verbal cues (the words "front" or "back") in directing the participant's visual attention to the relevant direction. The results suggest that spatially predictive semantically meaningful auditory warning signals may provide a particularly effective means of capturing attention.