Symbolic Signal Use in Wild Chimpanzee Gestural Communication?: A Theoretical Framework

Symbolic communication is not obvious in the natural communicative repertoires of our closest living relatives, the great apes. However, great apes do show symbolic competencies in laboratory studies. This includes the understanding and the use of human-provided abstract symbols. Given this evidence for the underlying ability, the apparent failure to make use of it in the wild is puzzling. We provide a theoretical framework for identifying basic forms of symbolic signal use in chimpanzee natural communication. In line with the laboratory findings, we concentrate on the most promising domain to investigate, namely gesture, and we provide a case study in this area. We suggest that evidence for basic symbolic signal use would consist of the presence of two key characteristics of symbolic communication, namely arbitrariness and conventionalization. Arbitrariness means that the linkage between the form of the gesture and its meaning shows no obvious logical or otherwise motivated connection. Conventionalization means that the gesture is shared at the group-level and is thus socially learned, not innate. Further, we discuss the emergence and transmission of these gestures. Demonstrating this basic form of symbolic signal use would indicate that the symbolic capacities revealed by laboratory studies also find their expression in the natural gestural communication of our closest living relatives, even if only to a limited extent. This theoretical article thus aims to contribute to our understanding of the developmental origins of great ape gestures, and hence, arguably, of human symbolic communication. It also has a very practical aim in that by providing clear criteria and by pointing out potential candidates for symbolic communication, we give fieldworkers useful prerequisites for identifying and analyzing signals which may demonstrate the use of great apes’ symbolic capacities in the wild.

Pattern Recognition of Grating Perimeter Intrusion Behavior in Deep Learning Method

An intrusion behavior recognition method based on deep learning is proposed in this paper in order to improve the recognition accuracy of raster perimeter intrusion behavior. The Mach–Zehnder fiber optic interferometer was used to collect the external vibration signal sensing unit, capture the external vibration signal, use the cross-correlation characteristic method to obtain the minimum frame length of the fiber vibration signal, and preprocess the intrusion signal according to the signal strength. The intrusion signals were superimposed and several sections of signals were intercepted by fixed window length; the spectrum information is obtained by Fourier transform of the intercepted stationary signals. The convolution neural network was introduced into the pattern recognition of the intrusion signals in the optical fiber perimeter defense zone, and the different characteristics of the intrusion signals were extracted, so as to realize the accurate identification of different intrusion signals. Experimental results showed that this method was highly sensitive to intrusion events, could effectively reduce the false alarm rate of intrusion signals, and could improve the accuracy and efficiency of intrusion signal recognition.

Multiple sensory modalities in diurnal geckos is associated with the signalling environment and evolutionary constraints

To be effective, animal signals need to be detectable in the environment, but their development and expression require resources. For multimodal communication, investment in elaborating traits in one modality could reduce the elaboration of traits in other modalities. In Cnemaspis geckos, chemical signals for conspecific communication pre-dated the evolution of visual signals, allowing us to examine the potential trade-off in signal elaboration and the current habitat associations with signal use. We studied five species of Cnemaspis and quantified visual (patch size, colour characteristics) and chemical (secretory composition) traits in males, as well as key environmental parameters (temperature, humidity, light) in each of their habitats. Within species, we found some trade-off in the elaboration of signals, as the strength of several components in the visual and chemical modalities were negatively associated. Strength of some signal components in each modality was also independently associated with specific environmental parameters that affect their detection (visual traits) and persistence (chemical traits). Specifically, species with larger, brighter, and more saturated colour patches were found in habitats where the brightness and chroma of light were lower. Furthermore, environments with higher substrate temperature and higher relative humidity harboured species that produced secretions with a higher percentage of saturated and aromatic compounds. Thus, the elaboration of multimodal signals in this group of Cnemaspis geckos seem to increase efficiency of communication in the signalling-environment, but the strength of signals in different modalities are constrained by trade-offs in signal expression.

Quantifying Facial Expression Intensity and Signal Use in Deaf Signers

We live in a world of rich dynamic multisensory signals. Hearing individuals rapidly and effectively integrate multimodal signals to decode biologically relevant facial expressions of emotion. Yet, it remains unclear how facial expressions are decoded by deaf adults in the absence of an auditory sensory channel. We thus compared early and profoundly deaf signers (n = 46) with hearing nonsigners (n = 48) on a psychophysical task designed to quantify their recognition performance for the six basic facial expressions of emotion. Using neutral-to-expression image morphs and noise-to-full signal images, we quantified the intensity and signal levels required by observers to achieve expression recognition. Using Bayesian modeling, we found that deaf observers require more signal and intensity to recognize disgust, while reaching comparable performance for the remaining expressions. Our results provide a robust benchmark for the intensity and signal use in deafness and novel insights into the differential coding of facial expressions of emotion between hearing and deaf individuals.

The loud scratch: a newly identified gesture of Sumatran orangutan mothers in the wild

The communicative function of primates' self-directed behaviours like scratching has gained increasing attention in recent years, but their intentional use is still debated. Here, we addressed this issue by exploring the communicative function of ‘loud scratches’ in wild Sumatran orangutans. Building on previous studies in chimpanzees, we examined the prediction that audio-visual loud scratches are used communicatively in mother–infant travel coordination. Specifically, we examined whether individual, social and scratch features affected the use of pre-move scratches, markers of intentional signal use and approach responses. We analysed a total of 1457 scratching bouts, produced by 17 individuals (including four mothers and their dependent offspring) observed during 305 h of focal follows. Overall, we found that scratching bouts preceded departure mainly when these were produced by mothers and showed features of exaggeration. If the scratching individual was a mother, associates were more likely to be visually attentive during pre-move scratches than in other contexts. Approach or follow responses to scratches by individuals in association were predicted by context, the relationship with the scratcher (i.e. offspring) and the associate's attentional state. We conclude that orangutan mothers use loud scratches as communicative strategies to coordinate joint travel with their infants.

Patterns of Cyclist and Pedestrian Street Crossing Behavior and Safety on an Urban Greenway

Greenways are linear open spaces, which are often used as trails for pedestrians and cyclists, but junctions with roads are a safety concern and act as a potential impediment to active transportation. This study evaluated crossing behavior patterns and safety at greenway–road junctions in New Orleans, LA. Crossing behaviors, safety and motor vehicle behavior were collected using direct observation methods. Intercept surveys were conducted to assess greenway use and safety perceptions. Logistic and negative binomial regression were used to assess the relationships between crossing signal (rectangular rapid flash beacon) activation and motor vehicle behavior. Fewer unsafe crossings occurred when the crossing signals were activated for cyclists and pedestrians (p-values of 0.001 and 0.01, respectively). There was no association between pedestrian use of crossing signals and motor vehicle stopping behavior but cyclists had significantly higher odds of motor vehicles failing to stop when the signal was activated (OR 5.12, 95% CI 2.86–9.16). The activation of rectangular rapid flash beacons at urban greenway junctions with roads did not influence motor vehicle behavior. Differences in crossing safety by signal use cannot be attributed to the signal’s influence on motor vehicle stopping behavior.