Emotional contagion or sensitivity to behavior in ravens?

I commend Adriaense et al. (1) for studying emotional contagion by cleverly using the judgment bias paradigm to assess emotional states in ravens who have experienced a manipulation vicariously. This construct is controversial, especially with regard to its relationship to empathy (2). Sensitivity to the behaviors of others does not indicate acknowledgment of or concern for the emotions of others. The authors are careful to frame as observers being “attentive to the demonstrators’ behavioral expressions” rather than to their emotions, but this should leave the reader wondering what exactly is being assessed. Ravens may recognize cues that something pleasant or aversive is about to occur. Because the researchers found negative bias only in the negative condition but no evidence of positive bias in the positive condition, it seems that ravens were less optimistic about receiving a reward in conditions where there were no behavioral cues of reward anticipation.

Without confirming the emotional states of the demonstrators, it is not possible to claim that “an underlying negative affective state was transferred to the observer.” Although the authors collected data, which did not support the manipulation, they problematically claim it “unsuitable for interpretation.” It could be an expectation of reward that was transferred rather than an emotion. If birds observing a nonsocial control with cues predicting a negative outcome also showed a negative judgment bias, it would mitigate against emotional contagion as a mechanism, but unfortunately, no such control was presented.

Disentangling interpretations based on reasoning about behavioral versus mental states is a well-known problem in comparative psychology and not one that is resolved by the current paradigm. It is a subtle but important distinction to assume that animals are responding to others’ internal states rather than to behaviors alone; to experience emotional contagion implies that observers perceive others’ emotions. Demonstrator behaviors could have been associated with positive and negative outcomes.

There are no behavioral observations to validate the emotional states of observers, which is important because results of cognitive bias tests are open to interpretation and best used in conjunction with other measures of emotional state (3).

There are several other problematic methodological issues. The birds served as both demonstrators and observers, so they could have been responding to cues that reminded them of their own experience rather than relating to the emotional experience of the demonstrators.

There are many ambiguous trials (A) presented at a high ratio to positive (P) and negative (N) trials (32 P, 32 N, 24 A). Although the birds continued to respond to A, which the authors argue to mean that A did not lose its ambiguity, they also continued to respond to N, suggesting they did not fully learn when they would not receive a reward. It would be important to see responses across trials to detect changes over time and to determine whether the effects were driven by a small subset of birds.

The authors present a promising methodology that, with some tweaks, could inform the debate on emotional contagion in nonhumans.