The dynamics of apparent horizons in Robinson-Trautman spacetimes

We present an alternative scheme of finding apparent horizons based on spectral methods applied to Robinson-Trautman spacetimes. We have considered distinct initial data such as representing the spheroids of matter and the head-on collision of two non-rotating black holes. The evolution of the apparent horizon is presented. We have obtained in some cases a mass gap between the final Bondi and apparent horizon masses, whose implications were briefly commented in the light of the thermodynamics of black holes.Comment: 9 pages, 7 figure

High emotional contagion and empathy are associated with enhanced detection of emotional authenticity in laughter

Nonverbal vocalisations such as laughter pervade social interactions, and the ability to accurately interpret them is an important skill. Previous research has probed the general mechanisms supporting vocal emotional processing, but the factors that determine individual differences in this ability remain poorly understood. Here, we ask whether the propensity to resonate with others’ emotions—as measured by trait levels of emotional contagion and empathy—relates to the ability to perceive different types of laughter. We focus on emotional authenticity detection in spontaneous and voluntary laughs: spontaneous laughs reflect a less controlled and genuinely felt emotion, and voluntary laughs reflect a more deliberate communicative act (e.g., polite agreement). In total, 119 participants evaluated the authenticity and contagiousness of spontaneous and voluntary laughs and completed two self-report measures of resonance with others’ emotions: the Emotional Contagion Scale and the Empathic Concern scale of the Interpersonal Reactivity Index. We found that higher scores on these measures predict enhanced ability to detect laughter authenticity. We further observed that perceived contagion responses during listening to laughter significantly relate to authenticity detection. These findings suggest that resonating with others’ emotions provides a mechanism for processing complex aspects of vocal emotional information

Automaticity in the Recognition of Nonverbal Emotional Vocalizations

The ability to perceive the emotions of others is crucial for everyday social interactions. Important aspects of visual socioemotional processing, such as the recognition of facial expressions, are known to depend on largely automatic mechanisms. However, whether and how properties of automaticity extend to the auditory domain remains poorly understood. Here we ask if nonverbal auditory emotion recognition is a controlled deliberate or an automatic efficient process, using vocalizations such as laughter, crying, and screams. In a between-subjects design (N = 112), and covering eight emotions (four positive), we determined whether emotion recognition accuracy (a) is improved when participants actively deliberate about their responses (compared with when they respond as fast as possible) and (b) is impaired when they respond under low and high levels of cognitive load (concurrent task involving memorizing sequences of six or eight digits, respectively). Response latencies were also measured. Mixed-effects models revealed that recognition accuracy was high across emotions, and only minimally affected by deliberation and cognitive load; the benefits of deliberation and costs of cognitive load were significant mostly for positive emotions, notably amusement/laughter, and smaller or absent for negative ones; response latencies did not suffer under low or high cognitive load; and high recognition accuracy (approximately 90%) could be reached within 500 ms after the stimulus onset, with performance exceeding chance-level already between 300 and 360 ms. These findings indicate that key features of automaticity, namely fast and efficient/effortless processing, might be a modality-independent component of emotion recognition

Elevated arousal at time of decision-making is not the arbiter of risk avoidance in chickens

The somatic marker hypothesis proposes that humans recall previously experienced physiological responses to aid decision-making under uncertainty. However, little is known about the mechanisms used by non-human animals to integrate risk perception with predicted gains and losses. We monitored the behaviour and physiology of chickens when the choice between a high-gain (large food quantity), high-risk (1 in 4 probability of receiving an air-puff) option (HGRAP) or a low-gain (small food quantity), no-risk (of an air-puff) (LGNAP) option. We assessed when arousal increased by considering different stages of the decision-making process (baseline, viewing, anticipation, reward periods) and investigated whether autonomic responses influenced choice outcome both immediately and in the subsequent trial. Chickens were faster to choose and their heart-rate significantly increased between the viewing and anticipation (post-decision, pre-outcome) periods when selecting the HGRAP option. This suggests that they responded physiologically to the impending risk. Additionally, arousal was greater following a HGRAP choice that resulted in an air-puff, but this did not deter chickens from subsequently choosing HGRAP. In contrast to human studies, we did not find evidence that somatic markers were activated during the viewing period, suggesting that arousal is not a good measure of avoidance in non-human animals

Swordtail Fry Attend to Chemical and Visual Cues in Detecting Predators and Conspecifics

Predation pressure and energy requirements present particularly salient opposing selective pressures on young fish. Thus, fry are expected to possess sophisticated means of detecting predators and resources. Here we tested the hypotheses that fry of the swordtail fish Xiphophorus birchmanni use chemical and visual cues in detection of predators and conspecifics. To test these hypotheses we presented young (<7 day-old) fry with combinations of visual and chemical stimuli from adult conspecifics and predators. We found that exposure to predator odors resulted in shoal tightening similar to that observed when fry were presented with visual cues alone. In trials with conspecific stimuli, fry were particularly attracted to adult conspecifics when presented simultaneous visual and chemical stimuli compared to the visual stimulus alone. These results show that fry attend to the odors of adult conspecifics, whose presence in a particular area may signal the location of resources as well as an absence of predators. This is one of the first studies to show that such young fish use chemical and visual cues in predator detection and in interactions with conspecifics. Previous research in X. birchmanni has shown that anthropogenic alteration of the chemical environment disrupts intraspecific chemical communication among adults; we suggest that because fry use the same chemosensory pathways to detect predators and conspecifics, alteration of the chemical environment may critically disrupt predator and resource detection

Application and Validation of Case-Finding Algorithms for Identifying Individuals with Human Immunodeficiency Virus from Administrative Data in British Columbia, Canada

Objective To define a population-level cohort of individuals infected with the human immunodeficiency virus (HIV) in the province of British Columbia from available registries and administrative datasets using a validated case-finding algorithm. Methods Individuals were identified for possible cohort inclusion from the BC Centre for Excellence in HIV/AIDS (CfE) drug treatment program (antiretroviral therapy) and laboratory testing datasets (plasma viral load (pVL) and CD4 diagnostic test results), the BC Centre for Disease Control (CDC) provincial HIV surveillance database (positive HIV tests), as well as databases held by the BC Ministry of Health (MoH); the Discharge Abstract Database (hospitalizations), the Medical Services Plan (physician billing) and PharmaNet databases (additional HIV-related medications). A validated case-finding algorithm was applied to distinguish true HIV cases from those likely to have been misclassified. The sensitivity of the algorithms was assessed as the proportion of confirmed cases (those with records in the CfE, CDC and MoH databases) positively identified by each algorithm. A priori hypotheses were generated and tested to verify excluded cases. Results A total of 25,673 individuals were identified as having at least one HIV-related health record. Among 9,454 unconfirmed cases, the selected case-finding algorithm identified 849 individuals believed to be HIV-positive. The sensitivity of this algorithm among confirmed cases was 88%. Those excluded from the cohort were more likely to be female (44.4% vs. 22.5%; p&lt;0.01), had a lower mortality rate (2.18 per 100 person years (100PY) vs. 3.14/100PY; p&lt;0.01), and had lower median rates of health service utilization (days of medications dispensed: 9745/100PY vs. 10266/100PY; p&lt;0.01; days of inpatient care: 29/100PY vs. 98/100PY; p&lt;0.01; physician billings: 602/100PY vs. 2,056/100PY; p&lt;0.01). Conclusions The application of validated case-finding algorithms and subsequent hypothesis testing provided a strong framework for defining a population-level cohort of HIV infected people in BC using administrative databases

Threat-sensitive anti-predator defence in precocial wader, the northern lapwing Vanellus vanellus

Birds exhibit various forms of anti-predator behaviours to avoid reproductive failure, with mobbing—observation, approach and usually harassment of a predator—being one of the most commonly observed. Here, we investigate patterns of temporal variation in the mobbing response exhibited by a precocial species, the northern lapwing (Vanellus vanellus). We test whether brood age and self-reliance, or the perceived risk posed by various predators, affect mobbing response of lapwings. We quantified aggressive interactions between lapwings and their natural avian predators and used generalized additive models to test how timing and predator species identity are related to the mobbing response of lapwings. Lapwings diversified mobbing response within the breeding season and depending on predator species. Raven Corvus corax, hooded crow Corvus cornix and harriers evoked the strongest response, while common buzzard Buteo buteo, white stork Ciconia ciconia, black-headed gull Chroicocephalus ridibundus and rook Corvus frugilegus were less frequently attacked. Lapwings increased their mobbing response against raven, common buzzard, white stork and rook throughout the breeding season, while defence against hooded crow, harriers and black-headed gull did not exhibit clear temporal patterns. Mobbing behaviour of lapwings apparently constitutes a flexible anti-predator strategy. The anti-predator response depends on predator species, which may suggest that lapwings distinguish between predator types and match mobbing response to the perceived hazard at different stages of the breeding cycle. We conclude that a single species may exhibit various patterns of temporal variation in anti-predator defence, which may correspond with various hypotheses derived from parental investment theory

The importance of indirect cues for white-browed sparrow-weaver (Plocepasser mahali) risk assessment

Both direct cues that provide information about the actual presence of a predator and indirect environmental cues that provide information about the probability of encountering a predator may be used by animals assessing predation risk, but relatively few studies manipulate both simultaneously to study their relative importance. We conducted two experiments to study the foraging decisions of white-browed sparrow-weavers (Plocepasser mahali). The first experiment manipulated both direct and indirect cues in a feeding array by simultaneously placing feeding stations at different distances from humans (to manipulate direct risk) and from protective cover (to manipulate indirect risk). Weaver foraging was influenced more by indirect risk than by direct risk. The second experiment aimed to determine if weaver’s indirect risk assessment was sensitive to variation in benefits. We set two feeding stations at different distances from cover but the same distance from the human observers and systematically increased the amount of food at the station farther from cover. Weavers far from cover initially foraged at higher rates than those close to cover, but the addition of food reduced the foraging rate. Together, our results illustrate that weaver foraging decisions are sensitive to variation in risk and that indirect cues are relatively more important than direct cues