Negative emotional contagion and cognitive bias in common ravens (Corvus corax)

Abstract

Emotional contagion is described as an emotional state matching between subjects, and has been suggested to facilitate communication and coordination in complex social groups. Empirical studies typically focus on the measurement of behavioral contagion and emotional arousal, yet, while highly important, such an approach often disregards an additional evaluation of the underlying emotional valence. Here, we studied emotional contagion in ravens by applying a judgment bias paradigm to assess emotional valence. We experimentally manipulated positive and negative affective states in demonstrator ravens, to which they responded with increased attention and interest in the positive condition, as well as increased redirected behavior and a left-eye lateralization in the negative condition. During this emotion manipulation, another raven observed the demonstrator's behavior, and we used a bias paradigm to assess the emotional valence of the observer to determine whether emotional contagion had occurred. Observers showed a pessimism bias toward the presented ambiguous stimuli after perceiving demonstrators in a negative state, indicating emotional state matching based on the demonstrators' behavioral cues and confirming our prediction of negative emotional contagion. We did not find any judgment bias in the positive condition. This result critically expands upon observational studies of contagious play in ravens, providing experimental evidence that emotional contagion is present not only in mammalian but also in avian species. Importantly, this finding also acts as a stepping stone toward understanding the evolution of empathy, as this essential social skill may have emerged across these taxa in response to similar socioecological challenges.

Keywords: animal emotion; avian empathy; cognitive bias paradigm; emotional contagion.

Fig. 1.

Experimental procedure. The procedure consists chronologically of a discrimination training before the experiment (1), a premanipulation cognitive bias test (2), a positive or negative emotion manipulation of the demonstrator (3), and a postmanipulation bias test (4).

Fig. 2.

Demonstrator behavior. Predicted behavioral responses (mean ± SE) for an average demonstrator before and after the positive and negative conditions, including locomotion (A), time spent in front of the food items (B), head and body movements (C), redirected behavior (D), and left-eye use upon inspecting the food items (E). Note that A, C, and D are count frequencies, while B and E are duration proportions (s). Planned comparisons were conducted within conditions from phase 1 to phase 3 and between positive and negative conditions for phase 3 (see SI Appendix, Table S2 for further details). *P < 0.05; **P ≤ 0.01.

Fig. 3.

Observer cognitive bias test. Predicted latencies to peck (mean ± SE) for an average observer raven in an average dyad at each location across the positive and negative conditions. We conducted planned comparisons of observer response latencies at each location before (full line) and after (dotted line) the emotion manipulations (see SI Appendix, Table S3 for further details). *P ≤ 0.05.