Robustness of early warning signals of regime shifts in time-delayed ecological models

Various ecological and other complex dynamical systems may exhibit abrupt regime shifts or critical transitions, wherein they reorganize from one stable state to another over relatively short time scales. Because of potential losses to ecosystem services, forecasting such unexpected shifts would be valuable. Using mathematical models of regime shifts, ecologists have proposed various early warning signals of imminent shifts. However, their generality and applicability to real ecosystems remain unclear because these mathematical models are considered too simplistic. Here, we investigate the robustness of recently proposed early warning signals of regime shifts in two well-studied ecological models, but with the inclusion of time-delayed processes. We find that the average variance may either increase or decrease prior to a regime shift and, thus, may not be a robust leading indicator in time-delayed ecological systems. In contrast, changing average skewness, increasing autocorrelation at short time lags, and reddening power spectra of time series of the ecological state variable all show trends consistent with those of models with no time delays. Our results provide insights into the robustness of early warning signals of regime shifts in a broader class of ecological systems.

Early Warning Signals of Ecological Transitions: Methods for Spatial Patterns

A number of ecosystems can exhibit abrupt shifts between alternative stable states. Because of their important ecological and economic consequences, recent research has focused on devising early warning signals for anticipating such abrupt ecological transitions. In particular, theoretical studies show that changes in spatial characteristics of the system could provide early warnings of approaching transitions. However, the empirical validation of these indicators lag behind their theoretical developments. Here, we summarize a range of currently available spatial early warning signals, suggest potential null models to interpret their trends, and apply them to three simulated spatial data sets of systems undergoing an abrupt transition. In addition to providing a step-by-step methodology for applying these signals to spatial data sets, we propose a statistical toolbox that may be used to help detect approaching transitions in a wide range of spatial data. We hope that our methodology together with the computer codes will stimulate the application and testing of spatial early warning signals on real spatial data.

Auditory distraction from low-intensity noise: a review of the consequences for learning and workplace environments

The 'irrelevant sound effect' in short-term memory is commonly believed to entail a number of direct consequences for cognitive performance in the office and other workplaces (e.g. S. P. Banbury, S. Tremblay, W. J. Macken, & D. M. Jones, 2001). It may also help to identify what types of sound are most suitable as auditory warning signals. However, the conclusions drawn are based primarily upon evidence from a single task (serial recall) and a single population (young adults). This evidence is reconsidered from the standpoint of different worker populations confronted with common workplace tasks and auditory environments. Recommendations are put forward for factors to be considered when assessing the impact of auditory distraction in the workplace. Copyright (c) 2005 John Wiley & Sons, Ltd.

Facilitatory effects of an auditory warning stimulus in a visual location identification task and a visual shape identification task

The occurrence of a weak auditory warning stimulus increases the speed of the response to a subsequent visual target stimulus that must be identified. This facilitatory effect has been attributed to the temporal expectancy automatically induced by the warning stimulus. It has not been determined whether this results from a modulation of the stimulus identification process, the response selection process or both. The present study examined these possibilities. A group of 12 young adults performed a reaction time location identification task and another group of 12 young adults performed a reaction time shape identification task. A visual target stimulus was presented 1850 to 2350 ms plus a fixed interval (50, 100, 200, 400, 800, or 1600 ms, depending on the block) after the appearance of a fixation point, on its left or right side, above or below a virtual horizontal line passing through it. In half of the trials, a weak auditory warning stimulus (S1) appeared 50, 100, 200, 400, 800, or 1600 ms (according to the block) before the target stimulus (S2). Twelve trials were run for each condition. The S1 produced a facilitatory effect for the 200, 400, 800, and 1600 ms stimulus onset asynchronies (SOA) in the case of the side stimulus-response (S-R) corresponding condition, and for the 100 and 400 ms SOA in the case of the side S-R non-corresponding condition. Since these two conditions differ mainly by their response selection requirements, it is reasonable to conclude that automatic temporal expectancy influences the response selection process.

Auditory message studies for route diversion. Final report.

Mode of access: Internet.

Further studies on auditory messages. Final report.

Mode of access: Internet.

Highway advisory radio in construction areas. Final report.

Mode of access: Internet.

Human factors requirements for real-time motorist information displays. Volume 5: bibliography and selected annotations: audio systems. Final report.

Federal Highway Administration, Office of Research, Washington, D.C.

Human factors requirements for real-time motorist information displays. Vol. 1 - design guide. Final report.

Federal Highway Administration, Office of Research, Washington, D.C.

The effect of perturbation warning on attention switching abilities during dual-task performance in young and older adults

This study examined whether providing an auditory warning would facilitate attention switching abilities in older adults during dual-tasking. Fifteen young and 16 older adults performed a tracking task while recovering their balance from a support surface translation. For half of the trials, an auditory warning was presented to inform participants of the upcoming translation. Performance was quantified through electromyographic (EMG) recordings of the lower limb muscles, while the ability to switch attention between tasks was determined by tracking task error. Providing warning of an upcoming loss of balance resulted in both young and older adults increasing their leg EMG activity by 10-165% (p<0.05) in preparation for the upcoming translation. However, no differences in the timing of attention switching were observed with or without the warning (p=0.424). Together, these findings suggest that providing a perturbation warning has minimal benefits in improving attention switching abilities for balance recovery in healthy older adults.

Programa de apoio a cuidadores: uma ação terapêutica e preventiva na atenção à saúde dos idosos

Dans le cadre du service de gériatrie du Centre de Santé-école de la faculté de médecine de Botucatu (Université de São Paulo), a été établi un programme d'appui à ces soignants avec les objectifs suivants: préserver leur qualité de vie et favoriser de meilleures conditions familiales aux patients. Le programme comprend de 10 à 12 réunions par semaine, de deux heures de durée, coordonnées par deux psychologues. on utilise des techniques de psychodrame centrées sur le rôle du soignant et leurs conséquences sociales et émotionnelles. Les informations théoriques sont transmises au moyen de discussions de groupe et de moyens audiovisuels. Les thèmes suivants sont abordés : signification et motivation du soin donné, signaux d'alertes de fatigue physique et mentale du soignant, les possibilités de se traiter et de demander de l'aide, une méthode d'amélioration de la communication face à une déficience visuelle, auditive et cognitive, une méthode pour favoriser l'indépendance et l'autonomie et surmonter les problèmes relatifs à l'hygiène, la mobilité, l'agression, l'irritation, les hallucinations et les idées délirantes de la personne âgée. Au cours de la première réunion de chaque groupe (qui comprend de 10 à 20 participants) on applique une échelle d'évaluation de l'impact émotionnel sur les soignants (Zarit et al., 1980) et le SRQ (Self Report Questionnaire - Mari and Williams, 1986) qui identifient des désordres psychiatriques. Ces échelles sont reproduites à la fin du programme, pour observer d'éventuelles modifications. Les données obtenues indiquent des changements favorables dans l'expression d'émotions, l'établissement de limites et de retour à des activités de loisirs.

Effects of visual and auditory stimuli in a choice reaction time task

The effect produced by a warning stimulus(i) (WS) in reaction time (RT) tasks is commonly attributed to a facilitation of sensorimotor mechanisms by alertness. Recently, evidence was presented that this effect is also related to a proactive inhibition of motor control mechanisms. This inhibition would hinder responding to the WS instead of the target stimulus (TS). Some studies have shown that auditory WS produce a stronger facilitatory effect than visual WS. The present study investigated whether the former WS also produces a stronger inhibitory effect than the latter WS. In one session, the RTs to a visual target in two groups of volunteers were evaluated. In a second session, subjects reacted to the visual target both with (50% of the trials) and without (50% of the trials) a WS. During trials, when subjects received a WS, one group received a visual WS and the other group was presented with an auditory WS. In the first session, the mean RTs of the two groups did not differ significantly. In the second session, the mean RT of the two groups in the presence of the WS was shorter than in their absence. The mean RT in the absence of the auditory WS was significantly longer than the mean RT in the absence of the visual WS. Mean RTs did not differ significantly between the present conditions of the visual and auditory WS. The longer RTs of the auditory WS group as opposed to the visual WS group in the WS-absent trials suggest that auditory WS exert a stronger inhibitory influence on responsivity than visual WS.

Maternal effects and the evolution of aposematic signals

Aposematic signals that warn predators of the noxious qualities of prey gain their greatest selective advantage when predators have already experienced similar signals. Existing theory explains how such signals can spread through selective advantage after they are present at some critical frequency, but is unclear about how warning signals can be selectively advantageous when the trait is initially rare (i.e., when it first arises through mutation) and predators are naive. When aposematism is controlled by a maternal effect gene, the difficulty of initial rarity may be overcome. Unlike a zygotically expressed gene, a maternally expressed aposematism gene will be hidden from selection because it is not phenotypically expressed in the first individual with the mutation. Furthermore, the first individual carrying the new mutation will produce an entire family of aposematic offspring, thereby providing an immediate fitness advantage to this gene.