Biology subjects

Dezecache, G.

Publications and source records attributed to Dezecache, G..

3 recordsLinked to original sources

bioRxiv2019

Early vocal production and functional flexibility in wild infant chimpanzees

How did human language evolve from earlier forms of communication? One way to address this question is to compare prelinguistic human vocal behavior with nonhuman primate calls. Here, an important finding has been that, prior to speech, human infant vocal behavior exhibits functional flexibility, the capacity of producing protophones that are not tied to one specific function. Nonhuman primate vocal behavior, by contrast, is comparably inflexible, with different call types tied to specific functions. Our research challenges the generality of this claim, with new findings of flexible vocal behavior in infant chimpanzees. We used artificial intelligence consisting of automated feature extraction and supervised learning algorithms to analyze grunt and whimper vocalizations from free-ranging infants during their first year of life. We found that grunt production was highly flexible occurring in positive, neutral and negative circumstances, as already shown in human infants. We also found acoustic variants of grunts produced in different affective contexts, suggesting gradation within this vocal category. By contrast, the second most common call type of infant chimpanzees, the whimpers, was produced in only one affective context in line with standard models of nonhuman primate vocal behavior. We concluded that the most common chimpanzee vocalization, the grunt, qualifies as functionally flexible, suggesting that evolution of vocal functional flexibility occurred before the split between the Homo and Pan lineages.

animal behavior and cognition↗

bioRxiv2019

Machine learning reveals adaptive maternal responses to infant distress calls in wild chimpanzees

Distress calls are an acoustically variable group of vocalizations ubiquitous in mammals and other animals. Their presumed function is to recruit help, but it is uncertain whether this is mediated by listeners extracting the nature of the disturbance from calls. To address this, we used machine learning to analyse distress calls produced by wild infant chimpanzees. It enabled us to classify calls and examine them in relation to the external event triggering them and the distance to the intended receiver, the mother. In further steps, we tested whether the acoustic variants produced by infants predicted maternal responses. Our results demonstrated that, although infant chimpanzee distress calls were highly graded, they conveyed information about discrete events, which in turn guided maternal parenting decisions. We discuss these findings in light of one the most vexing problems in communication theory, the evolution of vocal flexibility in the human lineage.

animal behavior and cognition↗

bioRxiv2019

The Threat of Scream paradigm: A tool for studying sustained physiological and subjective anxiety

Progress in understanding the emergence of pathological anxiety depends on the availability of paradigms effective in inducing anxiety in a simple, consistent and sustained way. Much progress has been made using the Threat-of-Shock paradigm (TOS), which generates anxiety through the delivery of unpredictable electric shocks to participants. However, TOS may be problematic when testing vulnerable populations. Moreover, it is not clear whether anxiety can be sustained throughout experiments of long duration. Here, we bring support for an alternative approach called the Threat-of-Scream paradigm (TOSc), in which the tactile delivery of shocks is replaced by the auditory delivery of distress screams. We report on an one-hour long study (plus its replication) in which participants were exposed to blocks before which they were told that they could hear aversive screams at any time (threat blocks), vs. blocks before which they were told that no scream will be heard (safe blocks). Both the experiment and its replication showed higher subjective reports of anxiety, higher skin conductance level, and positive correlation between the two measures, in threat compared to safe blocks. Anxiety measures were sustained throughout the experiments, suggesting little emotional and physiological habituation. Our results suggest that the delivery of low intensity distress screams can be an efficient, stable and cheap methodology to assess the impact of sustained anxiety on a diversity of cognitive functions and populations. We therefore believe the TOSc will become an essential part of the psychological toolkit, particularly so for researchers interested in the emergence of pathological anxiety.

neuroscience↗