Salient Signals Research Articles

Distance-dependent pattern blending can camouflage salient aposematic signals.

The effect of viewing distance on the perception of visual texture is well known: spatial frequencies higher than the resolution limit of an observer's visual system will be summed and perceived as a single combined colour. In animal defensive colour patterns, distance-dependent pattern blending may allow aposematic patterns, salient at close range, to match the background to distant observers. Indeed, recent research has indicated that reducing the distance from which a salient signal can be detected can increase survival over camouflage or conspicuous aposematism alone. We investigated whether the spatial frequency of conspicuous and cryptically coloured stripes affects the rate of avian predation. Our results are consistent with pattern blending acting to camouflage salient aposematic signals effectively at a distance. Experiments into the relative rate of avian predation on edible model caterpillars found that increasing spatial frequency (thinner stripes) increased survival. Similarly, visual modelling of avian predators showed that pattern blending increased the similarity between caterpillar and background. These results show how a colour pattern can be tuned to reveal or conceal different information at different distances, and produce tangible survival benefits.

Accent detection and social cognition: evidence of protracted learning.

How and when do children become aware that speakers have different accents? While adults readily make a variety of subtle social inferences based on speakers' accents, findings from children are more mixed: while one line of research suggests that even infants may be acutely sensitive to accent unfamiliarity, other studies suggest that 5-year-olds have difficulty identifying accents as different from their own. In an attempt to resolve this paradox, the current study assesses American children's sensitivity to American vs. Dutch accents in two situations. First, in an eye-tracked sentence processing paradigm where children have previously shown sensitivity to a salient social distinction (gender) from voice cues, 3-5-year-old children showed no sensitivity to accent differences. Second, in a social decision-making task where accent sensitivity has been found in 5-year-olds, an age gradient appeared, suggesting that familiar accent preferences emerge slowly between 3 and 7years. Counter to claims that accent is an early, salient signal of social group, results are more consistent with a protracted learning hypothesis that children need extended exposure to native-language sound patterns in order to detect that an accent deviates from their own. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=BQAgy3IFYXA.

Vocal performance is a salient signal for male–male competition in White-crowned Sparrows

ABSTRACT Vocal communication in songbirds is important for aggressive signaling, such that an honest signal allows receivers to assess a competitor's qualities. One aspect of song that conspecifics may assess is vocal performance. An example of vocal performance is how well an individual performs the trade-off between trill rate and bandwidth in production of repeated notes. This type of vocal performance (vocal deviation) is thought to be an honest signal because a male's ability to maximize both bandwidth and trill rate is limited by motor constraints on sound modification. Further, how well a male can repeat this trade-off may provide receivers with information about the signaler, and a male's own level of vocal performance can affect the strength of response to high-performance songs. We tested whether males assess each other based on vocal performance in an important model species, the White-crowned Sparrow (Zonotrichia leucophrys). We show that male White-crowned Sparrows respond more strongly to hi...

Perceived Synchrony of Frog Multimodal Signal Components IsInfluenced by Content and Order.

Multimodal signaling is common in communication systems. Depending on the species, individual signal components may be produced synchronously as a result of physiological constraint (fixed) or each component may be produced independently (fluid) in time. For animals that rely on fixed signals, a basic prediction is that asynchrony between the components should degrade the perception of signal salience, reducing receiver response. Male túngara frogs, Physalaemus pustulosus, produce a fixed multisensory courtship signal by vocalizing with two call components (whines and chucks) and inflating a vocal sac (visual component). Using a robotic frog, we tested female responses to variation in the temporal arrangement between acoustic and visual components. When the visual component lagged a complex call (whine + chuck), females largely rejected this asynchronous multisensory signal in favor of the complex call absent the visual cue. When the chuck component was removed from one call, but the robofrog inflation lagged the complex call, females responded strongly to the asynchronous multimodal signal. When the chuck component was removed from both calls, females reversed preference and responded positively to the asynchronous multisensory signal. When the visual component preceded the call, females responded as often to the multimodal signal as to the call alone. These data show that asynchrony of a normally fixed signal does reduce receiver responsiveness. The magnitude and overall response, however, depend on specific temporal interactions between the acoustic and visual components. The sensitivity of túngara frogs to lagging visual cues, but not leading ones, and the influence of acoustic signal content on the perception of visual asynchrony is similar to those reported in human psychophysics literature. Virtually all acoustically communicating animals must conduct auditory scene analyses and identify the source of signals. Our data suggest that some basic audiovisual neural integration processes may be at work in the vertebrate brain.

Duration of motherhood has incremental effects on mothers\u2019 neural processing of infant vocal cues: a neuroimaging study of women

The transition to motherhood, and the resultant experience of caregiving, may change the way women respond to affective, infant signals in their environments. Nonhuman animal studies have robustly demonstrated that mothers process both infant and other salient signals differently from nonmothers. Here, we investigated how women with and without young infants respond to vocalisations from infants and adults (both crying and neutral). We examined mothers with infants ranging in age (1–14 months) to examine the effects of duration of maternal experience. Using functional magnetic resonance imaging, we found that mothers showed greater activity than nonmothers to vocalisations from adults or infants in a range of cortical regions implicated in the processing of affective auditory cues. This main effect of maternal status suggests a general difference in vocalisation processing across infant and adult sounds. We found that a longer duration of motherhood, and therefore more experience with an infant, was associated with greater infant-specific activity in key parental brain regions, including the orbitofrontal cortex and amygdala. We suggest that these incremental differences in neural activity in the maternal brain reflect the building of parental capacity over time. This is consistent with conceptualizations of caregiving as a dynamic, learning process in humans.

The Merit Economy

A number of studies report, that remuneration - in addition to being a carrier of exchange value - has also signaling component, perceived by workers as a measure of their competence, social rank, or appreciation from society. Empirical and experimental evidence also suggests, that the signaling function is more reliable predictor of the workers’ economic performance, than its exchange value. The first claim of the presented paper is that decoupling the two functions into separate rewards can address certain problems associated with the existing remuneration mechanism, in particular distribution of exchange value, leading to income inequality. In the second claim, the common assumption concerning profit ownership is challenged, by pointing out that profit is not the result of a worker’s effort and therefore its exchange value should be shared in accordance with Rawls’s 2nd principle of justice. At the same time the motivationally salient signaling component of profit is not to be distributed, as it is measure of the rewarded worker’s intrinsic abilities. In the second part of the paper, framework of an economic system is proposed, based on these ideas.

Salient object changes influence overt attentional prioritization and object-based targeting in natural scenes.

A change to an object in natural scenes attracts attention when it occurs during a fixation. However, when a change occurs during a saccade, and is masked by saccadic suppression, it typically does not capture the gaze in a bottom-up manner. In the present work, we investigated how the type and direction of salient changes to objects affect the prioritization and targeting of objects in natural scenes. We asked observers to look around a scene in preparation for a later memory test. After a period of time, an object in the scene was increased or decreased in salience either during a fixation (with a transient signal) or during a saccade (without transient signal), or it was not changed at all. Changes that were made during a fixation attracted the eyes both when the change involved an increase and a decrease in salience. However, changes that were made during a saccade only captured the eyes when the change was an increase in salience, relative to the baseline no-change condition. These results suggest that the prioritization of object changes can be influenced by the underlying salience of the changed object. In addition, object changes that occurred with a transient signal (which is itself a salient signal) resulted in more central object targeting. Taken together, our results suggest that salient signals in a natural scene are an important component in both object prioritization and targeting in natural scene viewing, insofar as they align with object locations.

Anhedonia and Abstinence as Predictors of the Subjective Pleasantness of Positive, Negative, and Smoking-Related Pictures.

Anhedonia-diminished interest or pleasure in response to rewards-is a dimension implicated in several psychiatric disorders linked to smoking. This laboratory study sought to identify motivational mechanisms linking anhedonia and tobacco addiction by testing the hypothesis that anhedonia, abstinence, and their interaction would predict excesses and deficits in the perceived pleasantness of smoking-related and positive pictures, respectively. We assessed the pleasantness of negative pictures as a secondary outcome. After a baseline session involving self-report measures of anhedonia and other factors, 125 regular smokers attended two counterbalanced experimental sessions (overnight abstinent and non-abstinent) at which they rated the pleasantness of positive, smoking-related, negative, and neutral (control) pictures presented via computer. The difference in pleasantness ratings of positive, smoking-related, and negative pictures relative to neutral pictures served as the index of participants' appraisal of the motivational salience of nondrug reward, drug reward, and aversive signals, respectively. With and without adjusting for sex and depressive symptoms, greater anhedonia significantly or marginally predicted greater pleasantness of smoking (vs. neutral), lower pleasantness of positive (vs. neutral), less unpleasantness of negative (vs. neutral) pictures (|βs| = 0.18 to 0.35, ps = .007 to .07). Anhedonia by abstinence interaction effects on pleasantness ratings of each stimulus category (vs. neutral) were not significant (|βs| ≤ 0.02, ps ≥ .36). Anhedonia and abstinence additively increase the salience of smoking-related cues in anhedonic smokers. Smoking cessation efforts that attenuate sensitization to smoking stimuli may benefit anhedonic smokers early in quit attempts. Taken together, these findings provide tentative evidence that anhedonia is associated with a relative imbalance in the motivational salience of drug relative to nondrug rewards and may be associated with a generalized hypo-reactivity to both positive and negative stimuli. Though some prior smoking research has evidenced this relative imbalance in anhedonia with self-report or a smoking-choice task, we additionally show that this pattern may extend to hyper-affective reactivity to smoking-related stimuli being coincident with hypo-affective reactivity to nondrug-related positive stimuli (ie, may extend to greater pleasantness ratings of smoking pictures being accompanied by lower pleasantness ratings of positive pictures).

The relative response of songbirds to shifts in song amplitude and song minimum frequency

Lay Summary Male birds adjust their strength of response to songs modified with increased amplitude and minimum frequency in the presence of loud human noise. In addition, territorial rival males respond more strongly to louder songs than songs with relatively lower minimum frequencies. Thus, increasing song amplitude can compensate for any loss in signal salience due to shifting songs up in minimum frequency. Increasing only song minimum frequency in the context of high noise levels could be maladaptive.

Sustained, not habituated, activity in the human amygdala: A pilot fMRI dot-probe study of attentional bias to fearful faces

AbstractThe human amygdala consciously and nonconsciously processes facial expressions and directs spatial attention to them. Research has shown that amygdala activity habituates after repeated exposure to emotionally salient stimuli during passive viewing tasks. However, it is unclear to what extent the amygdala habituates during biologically relevant amygdala-mediated behaviors, such as the orienting of attention to environmentally salient social signals. The present study investigated amygdala habituation during a dot-probe task measuring attentional bias to backward masked fearful faces. The results suggest that across the duration of the 50 min (1,098 trial) task both attentional bias behavior and amygdala activity were sustained—rather than habituated. Thus, these initial findings indicate that when biologically relevant behavior is sustained, so too is amygdala activation.

Control of deviations and prediction of surface roughness from micro machining of THz waveguides using acoustic emission signals

By using acoustic emission (AE) it is possible to control deviations and surface quality during micro milling operations. The method of micro milling is used to manufacture a submillimetre waveguide where micro machining is employed to achieve the required superior finish and geometrical tolerances. Submillimetre waveguide technology is used in deep space signal retrieval where highest detection efficiencies are needed and therefore every possible signal loss in the receiver has to be avoided and stringent tolerances achieved. With a sub-standard surface finish the signals travelling along the waveguides dissipate away faster than with perfect surfaces where the residual roughness becomes comparable with the electromagnetic skin depth. Therefore, the higher the radio frequency the more critical this becomes. The method of time-frequency analysis (STFT) is used to transfer raw AE into more meaningful salient signal features (SF). This information was then correlated against the measured geometrical deviations and, the onset of catastrophic tool wear. Such deviations can be offset from different AE signals (different deviations from subsequent tests) and feedback for a final spring cut ensuring the geometrical accuracies are met. Geometrical differences can impact on the required transfer of AE signals (change in cut off frequencies and diminished SNR at the interface) and therefore errors have to be minimised to within 1µm. Rules based on both Classification and Regression Trees (CART) and Neural Networks (NN) were used to implement a simulation displaying how such a control regime could be used as a real time controller, be it corrective measures (via spring cuts) over several initial machining passes or, with a micron cut introducing a level plain measure for allowing setup corrective measures (similar to a spirit level).

Responses to Predictable versus Random Temporally Complex Stimuli from Single Units in Auditory Thalamus: Impact of Aging and Anesthesia.

Older individuals compensate for impaired ascending acoustic information by increasing use of cortical cognitive and attentional resources. The interplay between ascending and descending influences in the thalamus may serve to enhance the salience of speech signals that are degraded as they ascend to the cortex. The present findings demonstrate that medial geniculate body units from awake rats show an age-related preference for predictable modulated signals relative to randomly presented signals, especially at higher, more challenging modulation frequencies. Conversely, units from anesthetized animals, with little top-down influences, strongly preferred randomly presented modulated sequences. These results suggest a neuronal substrate for an age-related increase in experience/attentional-based influences in processing temporally complex auditory information in the auditory thalamus.

Effects of Social Facilitation on Perceived Workload, Subjective Stress, and Vigilance-Related Anxiety

Vigilance, or sustained attention, refers to the capability of an individual to maintain attention to a stimulus over extended periods of time. Typically, vigilance tasks are associated with high levels of workload and stress, which manifests as less task engagement, and greater distress. Several factors have been shown to affect vigilance and its associated workload and stress (i.e. signal saliency, task difficulty, etc.). However, one factor that has been neglected in previous research on workload, stress, and anxiety is the presence of someone in a supervisory role during the task. Therefore, the purpose of the present investigation was to determine how the presence of a supervisory figure influenced perceived workload, stress, and anxiety that is associated with vigilance tasks. It was hypothesized that the presence of a supervisory figure would decrease workload and distress, and would increase the levels of anxiety, when compared to a non-supervisor.

A fast-saliency method for real-time infrared small target detection

Infrared small target detection plays an important role in applications including military reconnaissance, early warning and terminal guidance. In this paper, we present a fast method, called fast-saliency, with very low computational complexity, for real-time small target detection in single image frame under various complex backgrounds. Different from traditional algorithms, the proposed method is inspired by a recent research on visual saliency detection indicating that small salient signals could be well detected by a gradient enhancement operation combined with Gaussian smoothing, which is able to delineate regions of small targets in infrared images. Concisely, there are only four simple steps contained in fast-saliency. In order, they are gradient operation, square computation, Gaussian smoothing and automatic thresholding, representing the four procedures as highpass filtering, target enhancement, noise suppression and target segmentation, respectively. Especially, for the most crucial step, gradient operation, we innovatively propose a 5×5 facet kernel operator that holds the key for separating the small targets from backgrounds. To verify the effectiveness of our proposed method, a set of real infrared images covering typical backgrounds with sea, sky and ground clutters are tested in experiments. The results demonstrate that it outperforms the state-of-the-art methods not only in detection accuracy, but also in computation efficiency.

Investor attention to rounding as a salient forecast feature

Prior research suggests that investors focus on subsets of more salient information when making economic decisions. We extend this research by examining the variation in investor responses to a salient feature of analyst forecasts. We focus on the roundness of analyst forecasts as a salient signal of imprecision. We examine whether: (1) investors notice rounding, even though it is binary and potentially has limited information content, (2) the investor reaction to rounding is affected by its repetition, and (3) the investor reaction to rounding varies by investor type. We document a weaker market reaction to rounded forecasts than to non-rounded forecasts, which is consistent with investors using rounding as an indicator of lower forecast precision. The investor response to rounding is more pronounced in the presence of multiple rounded forecasts, disclosed in analyst reports simultaneously, and is attributed primarily to less sophisticated investors. We also provide evidence of investors’ delayed assimilation of the information contained in rounded forecasts subsequent to the forecast announcement date. Our results shed light on the scope of limited investor attention.

Text Matching as Image Recognition

Matching two texts is a fundamental problem in many natural language processing tasks. An effective way is to extract meaningful matching patterns from words, phrases, and sentences to produce the matching score. Inspired by the success of convolutional neural network in image recognition, where neurons can capture many complicated patterns based on the extracted elementary visual patterns such as oriented edges and corners, we propose to model text matching as the problem of image recognition. Firstly, a matching matrix whose entries represent the similarities between words is constructed and viewed as an image. Then a convolutional neural network is utilized to capture rich matching patterns in a layer-by-layer way. We show that by resembling the compositional hierarchies of patterns in image recognition, our model can successfully identify salient signals such as n-gram and n-term matchings. Experimental results demonstrate its superiority against the baselines.

Hippogate: a break-in from entorhinal cortex

Discrimination of neutral from harmful environments is important for survival. But how do salient contextual signals yield persisting memories? A study uncovers a circuit that increases the specificity of hippocampus-based memories.

Introduction to special issue: Social attention in mind and brain

In everyday life we need to attend selectively to many things—some may be indexed by salient physical signals (a bright light, a car moving) but others may be indexed by the social importance of th...

Targeted activation of the hippocampal CA2 area strongly enhances social memory.

Social cognition enables individuals to understand others’ intentions. Social memory is a necessary component of this process, for without it, subsequent encounters are devoid of any historical information. The CA2 area of the hippocampus, particularly the vasopressin 1b receptor (Avpr1b) expressed there, is necessary for memory formation. We used optogenetics to excite vasopressin terminals, originating from the hypothalamic paraventricular nucleus, in the CA2 of mice. This markedly enhanced their social memory if the stimulation occurred during memory acquisition, but not retrieval. This effect was blocked by a Avpr1b antagonist. Finally, this enhanced memory is resistant to the social distraction of an introduced second mouse, important for socially navigating populations of individuals. Our results indicate the CA2 can increase the salience of social signals. Targeted pharmacotherapy with Avpr1b agonists or deep brain stimulation of the CA2 are potential avenues of treatment for those with declining social memory as in various dementias.

Innate immune system activation by viral RNA: How to predict it?

The immune system is able to identify foreign pathogens via different pathways. In the case of viral infection, recognition of the viral RNA is a crucial step, and many efforts have been made to understand which features of viral RNA are detected by the immune system. The biased viral RNA composition, measured as host–virus nucleotidic divergence, or CpG enrichment, has been proposed as salient signal. Peculiar structural features of these RNA could also be related to the immune system activation. Here, we gather multiple datasets and proceed to a meta-analysis to uncover the best predictors of immune system activation by viral RNA. “A” nucleotide content and Minimum Folding Energy are good predictors, and are more easily generalized than more complex indicators suggested previously. As RNA composition and structure are highly correlated, we suggest further experiments on synthetic sequences to identify the viral RNA sensing mechanisms by immune system receptors.