Communication breakdown: Limits of spectro-temporal resolution for the perception of bat communication calls

During vocal communication, the spectro-temporal structure of vocalizations conveys important contextual information. Bats excel in the use of sounds for echolocation by meticulous encoding of signals in the temporal domain. We therefore hypothesized that for social communication as well, bats would excel at detecting minute distortions in the spectro-temporal structure of calls. To test this hypothesis, we systematically introduced spectro-temporal distortion to communication calls of Phyllostomus discolor bats. We broke down each call into windows of the same length and randomized the phase spectrum inside each window. The overall degree of spectro-temporal distortion in communication calls increased with window length. Modelling the bat auditory periphery revealed that cochlear mechanisms allow discrimination of fast spectro-temporal envelopes. We evaluated model predictions with experimental psychophysical and neurophysiological data. We first assessed bats’ performance in discriminating original versions of calls from increasingly distorted versions of the same calls. We further examined cortical responses to determine additional specializations for call discrimination at the cortical level. Psychophysical and cortical responses concurred with model predictions, revealing discrimination thresholds in the range of 8–15 ms randomization-window length. Our data suggest that specialized cortical areas are not necessary to impart psychophysical resilience to temporal distortion in communication calls.

Clause-initial Vs in sign languages: Scene-setters

In our study, we seek to determine for sign languages the conditions under which a predicate can precede all its arguments. We consider data from the sign languages of Australia, Brazil, Britain, the Netherlands, and Sweden, examining interviews (informative dialogues) and narratives (monologues). While pressures of visualization converge to make SOV and SVO the unmarked orders in sign languages for most predicates, existential and presentational predicates may appear in sentence-initial position. In such instances, the predicate is a scene-setter, establishing a broad understanding of how we are to interpret the event we are about to visualize. We argue that pressures of visualization are again at work. Since sign languages are largely iconic – where the articulation itself brings up visual images – there is a stronger pressure for them to align articulation with mental visualization than for spoken languages; the goal of clear communication calls for this alignment whenever possible.

Effects of Diaphorina citri Population Density on Daily Timing of Vibrational Communication Calls: Potential Benefits in Finding Forage

Adult Diaphorina citri (ACP) use visual and chemical cues to locate young citrus flush shoots on which they forage and oviposit, and they use vibrational communication duetting calls as cues to help locate mates. For individual pairs, calling and mating usually peaks between 10:00 and 15:00. To explore whether call rates (calls/h) are affected by interactions with nearby conspecifics, rates were compared in small citrus trees on which either 5 or 25 ACP female and male pairs had been released at 17:00 for later recording from sunrise (06:00) to 22:00. Final ACP locations were noted 40 h after release. Call rates were similar in both treatments during normal mating hours. However, rates were significantly higher for low- than high-density treatments between 06:00 and 10:00, which suggests calling during this period may be affected by conspecific density. Both sexes aggregated on flush at both densities. We discuss the potential that ACP producing calls near sunrise, outside of normal mating hours, might benefit from gains in reproductive fitness in low-density contexts if they call not only to locate mates but also to locate preferred flush—in which case, co-opting of vibrations to disrupt both mating and foraging may be feasible.

Evaluating Communication Effectiveness Through Eye Tracking: Benefits, State of the Art, and Unresolved Questions

Modern eye-tracking techniques have opened a new door of opportunities for evaluating communication effectiveness in a way that minimizes cognitive biases and provides moment-by-moment insights into communication’s attention processes. The increasing body of research applying eye-tracking methodologies, together with the reorientation of the landscape of communication, calls for a comprehensive overview of the scope of research concerning audience’s visual attention to advertising. This is the first study that applies a systematic literature review approach to face this research gap by analyzing 112 papers published between 1979 and 2019 in journals indexed by the ISI Web of Science database. Based on this review, the article examines current evidence determining the visual attention to ads and the relationship between eye-tracking measures and other facets of advertising effectiveness, namely cognitive, affective, and behavioral consumer response. Finally, this article discusses the implications for business communication and proposes directions for academics and professionals intending to explore advertising effectiveness through eye tracking.

Processing of fast amplitude modulations in bat auditory cortex matches communication call-specific sound features

Bats use a large repertoire of calls for social communication. In the bat Phyllostomus discolor, social communication calls are often characterized by sinusoidal amplitude and frequency modulations with modulation frequencies in the range of 100–130 Hz. However, peaks in mammalian auditory cortical modulation transfer functions are typically limited to modulation frequencies below 100 Hz. We investigated the coding of sinusoidally amplitude modulated sounds in auditory cortical neurons in P. discolor by constructing rate and temporal modulation transfer functions. Neuronal responses to playbacks of various communication calls were additionally recorded and compared with the neurons’ responses to sinusoidally amplitude-modulated sounds. Cortical neurons in the posterior dorsal field of the auditory cortex were tuned to unusually high modulation frequencies: rate modulation transfer functions often peaked around 130 Hz (median: 87 Hz), and the median of the highest modulation frequency that evoked significant phase-locking was also 130 Hz. Both values are much higher than reported from the auditory cortex of other mammals, with more than 51% of the units preferring modulation frequencies exceeding 100 Hz. Conspicuously, the fast modulations preferred by the neurons match the fast amplitude and frequency modulations of prosocial, and mostly of aggressive, communication calls in P. discolor. We suggest that the preference for fast amplitude modulations in the P. discolor dorsal auditory cortex serves to reliably encode the fast modulations seen in their communication calls. NEW & NOTEWORTHY Neural processing of temporal sound features is crucial for the analysis of communication calls. In bats, these calls are often characterized by fast temporal envelope modulations. Because auditory cortex neurons typically encode only low modulation frequencies, it is unclear how species-specific vocalizations are cortically processed. We show that auditory cortex neurons in the bat Phyllostomus discolor encode fast temporal envelope modulations. This property improves response specificity to communication calls and thus might support species-specific communication.

Bats adjust temporal features of echolocation calls but not those of communication calls in response to traffic noise

Summary statementThis study reveals the impact of anthropogenic noise on spectrally distinct vocalizations and the limitations of the acoustic masking hypothesis to explain the vocal response of bats to chronic noise.AbstractThe acoustic masking hypothesis states that auditory masking may occur if the target sound and interfering sounds overlap spectrally, and it suggests that animals exposed to noise will modify their acoustic signals to increase signal detectability. However, it is unclear if animals will put more effort into changing their signals that spectrally overlap more with the interfering sounds than when the signals overlap less. We examined the dynamic changes in the temporal features of echolocation and communication vocalizations of the Asian particolored bat (Vespertilio sinensis) when exposed to traffic noise. We hypothesized that traffic noise has a greater impact on communication vocalizations than on echolocation vocalizations and predicted that communication vocalization change would be greater than echolocation. The bats started to adjust echolocation vocalizations on the fourth day of noise exposure, including an increased number of call sequences, decreased number of calls, and vocal rate within a call sequence. However, there was little change in the duration of the call sequence. In contrast, these communication vocalization features were not significantly adjusted under noise conditions. These findings suggest that the degree of spectral overlap between noise and animal acoustic signals does not predict the level of temporal vocal response to the noise.