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Animals : an open access journal from MDPI2025; 15(21); 3217; doi: 10.3390/ani15213217

Chronic State and Relationship to Humans Influence How Horses Decode Emotions in Human Voices: A Brain and Behavior Study.

Abstract: Current research on acoustic encoding of emotional content suggests that there are universal cues, allowing for decoding within and across taxa. This is particularly important for human-animal relationships, wherein domestic animals are supposed to be particularly efficient in decoding human emotions. Here we investigated whether the decoding of the emotional content in human voices shared universal acoustic properties, or whether it could be influenced by experience. Emotional human voices were presented to two populations of horses, in which behavioral, cardiac, and brain responses were measured. The two populations differed in their living and working conditions: one population lived in naturalistic conditions (stable social groups in pastures) and were ridden occasionally for outdoor trail riding with one to a few different riders, while the other was kept in more restricted conditions (individual stalls) and participated in riding lessons involving many different riders. Assessment of the horses' welfare state (animal-based measures) and their relationships with humans, performed independently of the playback experiments, revealed that the populations differed in both aspects. Whereas both populations appeared to react to the angry human voice, the population with the best welfare state and relationship with humans showed little differentiation between the different emotional voices and exhibited low behavioral reactions. On the contrary, the other population showed high behavioral and cardiac reactions to all negative voices. Brain responses also differed, with the first population showing higher responses (increased gamma, i.e., excitation) for the happy voice and the second for fear and anger (increased theta, i.e., alarm). Thus, animals' affective state and past experiences appear very influential for their perception of (cross-taxa) acoustic emotional cues.
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Publication Date: 2025-11-05 PubMed ID: 41227547PubMed Central: PMC12610170DOI: 10.3390/ani15213217Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Research Overview

  • This study examined how horses decode emotional content in human voices and how this ability is influenced by their living conditions and relationships with humans.
  • Researchers measured behavioral, cardiac, and brain responses in two horse populations exposed to varied emotional human vocalizations.

Background and Purpose

  • Acoustic encoding of emotions is thought to contain universal cues that help decode emotions across different species.
  • Domestic animals like horses are proposed to be efficient in decoding human emotions due to close interactions with humans.
  • The study aimed to determine whether horses decode human emotional voices based on universal acoustic properties or if their learning and experience influence this decoding.

Subjects and Experimental Design

  • Two populations of horses were studied:
    • Population 1: Lived in naturalistic conditions with stable social groups on pastures; they were ridden occasionally by one to few familiar riders mainly for trail riding.
    • Population 2: Kept in more restricted conditions in individual stalls; participated in riding lessons with many different riders.
  • Researchers independently assessed:
    • The horses’ welfare state using animal-based measures.
    • The quality of the horses’ relationships with humans.
  • Both populations were exposed to human voices expressing different emotions (angry, happy, fear).
  • Behavioral changes, heart rate (cardiac response), and brain activity were recorded during the exposure.

Key Findings

  • Response to Angry Voices: Both populations reacted to angry human voices, indicating some universal recognition of negative emotions.
  • Differences in Emotional Differentiation and Reactivity:
    • Population 1 (better welfare and closer human relationship)
      • Showed little behavioral difference between different emotional voices.
      • Exhibited generally low behavioral reactivity.
      • Brain showed increased gamma waves, linked to excitation, in response to happy voices.
    • Population 2 (poorer welfare and varied human contact)
      • Exhibited strong behavioral and cardiac reactions to all negative voices (anger and fear).
      • Brain showed increased theta waves, indicative of alarm or heightened vigilance, especially for fear and anger voices.

Interpretation and Implications

  • The study reveals that horses do possess the ability to decode some emotional cues in human voices likely based on universal acoustic cues (e.g., recognizing anger).
  • However, this decoding is not purely innate or universal but is heavily influenced by the horses’ chronic affective state and their previous experiences with humans.
  • Horses in better welfare conditions and with stronger bonds to humans appear less reactive or more selective in their emotional responses, possibly due to habituation or better emotional regulation.
  • Conversely, horses in poorer welfare conditions and with more variable human contacts display heightened sensitivity and alarm responses to negative human emotions.
  • This underscores the importance of welfare and human-animal relationships in shaping how domestic animals perceive and respond to human emotional signals.

Broader Context

  • Findings support the idea that while there are cross-species emotional vocal cues, experience and individual emotional states modulate perception.
  • Enhanced understanding of emotional decoding in horses can improve training, welfare, and human-animal communication strategies.
  • The study contributes to ethology and animal cognition by integrating behavioral, physiological, and neurological data to explore emotion perception in non-human animals.

Cite This Article

APA
d'Ingeo S, Siniscalchi M, Quaranta A, Cousillas H, Hausberger M. (2025). Chronic State and Relationship to Humans Influence How Horses Decode Emotions in Human Voices: A Brain and Behavior Study. Animals (Basel), 15(21), 3217. https://doi.org/10.3390/ani15213217

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 15
Issue: 21
PII: 3217

Researcher Affiliations

d'Ingeo, Serenella
  • Animal Physiology and Behavior Research Unit, Department of Veterinary Medicine, University of Bari Aldo Moro, 70121 Bari, Italy.
  • Laboratoire Ethologie Animale et Humaine-EthoS, UMR 6552-CNRS, University of Rennes, 35042 Rennes Cedex, France.
Siniscalchi, Marcello
  • Animal Physiology and Behavior Research Unit, Department of Veterinary Medicine, University of Bari Aldo Moro, 70121 Bari, Italy.
Quaranta, Angelo
  • Animal Physiology and Behavior Research Unit, Department of Veterinary Medicine, University of Bari Aldo Moro, 70121 Bari, Italy.
Cousillas, Hugo
  • Laboratoire Ethologie Animale et Humaine-EthoS, UMR 6552-CNRS, University of Rennes, 35042 Rennes Cedex, France.
Hausberger, Martine
  • Integrative Neuroscience and Cognition Center, UMR 8002-CNRS, University of Paris-Cité, 75006 Paris, France.

Grant Funding

  • any specific number / Università Italo-Francese (UIF)

Conflict of Interest Statement

The authors declare no conflicts of interest.

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