Home Research Project Details C5 - Processing of graded signalling systems
Personal tools

C5 - Processing of graded signalling systems

Julia Fischer and Fred Wolf

A number of computational attempts have been made to describe the evolution of human speech from a theoretical point of view; these models typically assume discrete units and have been used to formulate hypotheses regarding the evolution of symbolic communication and grammar (Chater and Manning 2006; Chater et al. 2009; Komarova et al. 2001; Nowak et al. 2000). In order to understand the evolution of communication more generally, it is important to lift the characterization of the structure of other species’ vocal communication to a quantitative level. The vocal repertoires of most mammals consist of a limited number of call types that vary substantially within categories (‘call types’). These ‘graded signalling systems’ are supposed to be rich in information, but apparently exhibit increased uncertainty near category boundaries (Hammerschmidt and Fischer 2008; Marler et al. 1976). In the proposed project, we will empirically construct parameterized naturalistic repertoires of pseudo-vocalizations for the quantitative analysis of graded signal processing. To this end, will construct a signal parameterization that can cover natural individual variation and arousal based variation in animal calls, providing controlled ensembles of pseudo-vocalizations of varying degrees of gradation. We will obtain these parameterized vocal repertoires from a statistical analysis of previously established data corpora from nonhuman primates (e.g. > 30,000 calls from Barbary macaques) and from mice (> 50,000 ultrasonic vocalizations). The pseudo-vocalization ensembles will be used in acoustic analyses (Hammerschmidt and Fischer 1998). For highly graded signalling systems it may appear unavoidable that calls at category boundaries are difficult to categorize, despite of the general efficiency of categorical perception (Fischer 2006). While this has important implications for decision making processes, it also raises the hypothesis that for a species communicating with graded signalling systems, there is an evolutionary premium of producing sequences of calls (Arnold and Zuberbühler 2008). To assess this hypothesis, we will evaluate the information content of sequences and signal combinations. The insights gained from these analyses can then be tested in monkeys and mice (an increasingly important model organism for the study of animal vocalization and acoustic communication (Enard et al. 2009; Jamain et al. 2008)), using playback techniques that require no animal training (Fischer 1998; Fitch and Hauser 2004). Our results will provide a quantitative framework enabling to conceptualize the evolution of vocal communication at stages at which discrete signal repertoires and the opportunity to establish symbolic communication or even grammar do not yet exist.

Belongs to Group(s):
Cognitive Ethology, Theoretical Neurophysics

Is part of  Section C 

Members working within this Project:
Wolf, Fred 
Fischer, Julia  

Selected Publication(s):

Wadewitz, P, Hammerschmidt, K, Battaglia, D, Witt, A, Wolf, F, and Fischer, J (2015).
Characterizing Vocal Repertoires-Hard vs. Soft Classification Approaches
Plos One 10(4):e0125785, 1-16.