Animal Behavior, Computational Bioacoustics, Brains and Cognition

ABSTRACT The brain’s ability to associate information from different sensory modalities, known as cross-modal integration, is crucial for forming a coherent perception of objects and events. When such associations follow systematic and predictable patterns, they are referred to as cross-modal correspondences. Humans, for example, tend to associate large objects with low-pitched sounds and small objects with high-pitched sounds, a phenomenon known as pitch–size cross-modal correspondence. This phenomenon has been documented in several vertebrate species, yet direct experimental evidence in avian species remains comparatively limited. Here, we tested African penguins using a preferential choice paradigm in which individuals chose between two cubes of different sizes after hearing either a high- or low-pitched sound. Following passive exposure to congruent pitch–size pairings, penguins chose larger objects following low-pitched sounds and smaller objects following high-pitched sounds, indicating that auditory pitch guided their visual size choices. Given that individuals were pre-exposed to a limited set of pitch–size pairings, this effect may reflect either a preexisting bias consistent with cross-modal correspondences or the generalization of a learned association. Nevertheless, these findings demonstrate that penguins can integrate auditory and visual information to guide their behavior and generalize a systematic pitch–size relationship across sensory dimensions.

ABSTRACT Perceptual and sensorimotor events are often experienced as temporal patterns, that is, identified as sequences based on their temporal features. While current timing models propose separate mechanisms supporting the processing of single intervals and temporal patterns, they leave partially unclear whether the latter entails the processing of both individual intervals and the overall structure of a pattern, or only one of these features. Here, we narrowed this question down by investigating how violations of regularity within the individual intervals of a temporal sequence (i.e., local violations) and in its overall structure (i.e., global violations) differentially affect its reproduction. We tested these violation effects in three experiments in which the sequences were experienced either in the visual or auditory domain and had either simple or complex structures. Results showed that the precision in reproducing simple visual and auditory patterns was primarily affected by local violations, whereas global violations mostly impacted the reproduction of visual patterns with complex structures. These detrimental effects were partially explained by rescaling and bias effects in the reproduced patterns. Overall, our findings indicate that the processing and reproduction of temporal patterns differentially weigh individual intervals and global structure, depending on sensory modality and, for visual patterns, on structural complexity. , Our experience of the world is inherently structured by temporal patterns. Yet a full understanding of how we process such patterns is still lacking. Across three finger-tapping experiments employing the local–global paradigm, we show that the processing and reproduction of temporal patterns rely on a differential weighting of their individual elements and overall structure. This weighting depends on both the structural complexity of the patterns and the sensory modality in which they are experienced.

Abstract Vocal individuality has important biological functions in mammals: at crucial stages of development, it ensures feeding and is a prerequisite for auditory-based mother–pup recognition. Is vocal individuality only shaped by maturation or also by the degree of conspecific acoustic input? Here, we test how the neonatal auditory environment shapes development and individualization of calls in harbour seal pups (Phoca vitulina). To simulate low- versus high-conspecific acoustic density, 18 pups heard playbacks of calls from either 2 or 30 conspecifics. We recorded calls before and after playback exposure and extracted 12 acoustic parameters. Supervised machine learning and discriminant function analyses showed greater individual distinctiveness in both groups after playback, indicating a developmental trend toward individualization. Notably, pups exposed to less-variable input showed higher individuality. Euclidean distances on call parameters showed that both groups diverged from the playback signals. Distances on within-pup and between-pups housed together revealed opposite trajectories in the two groups: after the exposure, less-variable auditory input determined steadier individual calls, while more-variable auditory input scattered calls across the acoustic space. Altogether, our findings indicate that auditory input modulates vocal development in pups, making harbour seals a promising model for unravelling how neonatal environment affects vocal plasticity in a non-human mammal. This article is part of the theme issue ‘Mechanisms of learning from social interaction’.

Abstract Rhythm is ubiquitous in human culture and in nature, but hard to capture in all its complexity. A key dimension of rhythm, integer ratio categories occur when the relationship between temporal intervals can be expressed as small-integer ratios. Recent work has found integer ratio categories in most human musical cultures and some animal species’ vocalizations or behavioral displays. But biological systems are noisy, and empirically measured intervals rarely form an exact small-integer ratio. Here, we mathematically assess whether a leading integer ratio analysis method makes valid statistical and biological assumptions. In particular, we (1) make the temporal properties of empirical ratios explicit, both in general and for the typical use in the literature; (2) show how the choice of ratio formula affects the probability distribution of rhythm ratios and ensuing statistical results; (3) guide the reader to carefully consider the assumptions and null hypotheses of the statistical analysis; and (4) present a comprehensive methodology to statistically test integer ratios for any null hypothesis of choice. Our observations have implications for both past and future research in music cognition and animal behavior: They suggest how to interpret past findings and provide tools to choose the correct null hypotheses in future empirical work.