Abstract: This paper reviews evidence that increases the probability that many animals experience at least simple levels of consciousness. First, the search for neural correlates of consciousness has not found any consciousness-producing structure or process that is limited to human brains. Second, appropriate responses to novel challenges for which the animal has not been prepared by genetic programming or previous experience provide suggestive evidence of animal consciousness because such versatility is most effectively organized by conscious thinking. For example, certain types of classical conditioning require awareness of the learned contingency in human subjects, suggesting comparable awareness in similarly conditioned animals. Other significant examples of versatile behavior suggestive of conscious thinking are scrub jays that exhibit all the objective attributes of episodic memory, evidence that monkeys sometimes know what they know, creative tool-making by crows, and recent interpretation of goal-directed behavior of rats as requiring simple nonreflexive consciousness. Third, animal communication often reports subjective experiences. Apes have demonstrated increased ability to use gestures or keyboard symbols to make requests and answer questions; and parrots have refined their ability to use the imitation of human words to ask for things they want and answer moderately complex questions. New data have demonstrated increased flexibility in the gestural communication of swarming honey bees that leads to vitally important group decisions as to which cavity a swarm should select as its new home. Although no single piece of evidence provides absolute proof of consciousness, this accumulation of strongly suggestive evidence increases significantly the likelihood that some animals experience at least simple conscious thoughts and feelings. The next challenge for cognitive ethologists is to investigate for particular animals the content of their awareness and what life is actually like, for them.

Abstract: Animals frequently use signals that travel further than the spacing between individuals. For every intended recipient of a given signal there are likely to be many other individuals that receive information. Eavesdropping on signalling interactions between other individuals provides a relatively cost-free method of assessing future opponents or mates. Male great tits (Parus major) extract relative information from such interactions between individuals unknown to them. Here, we show that male great tits can take information gathering a stage further and obtain more information about a previously unencountered intruder, by the hitherto unknown capability of combining information gathered by eavesdropping with that derived from their own direct interaction with an individual. Prior experience with an intruder (A) was achieved by subjecting a focal male to different levels of intrusion simulated using interactive playback. This intruder (A) then took part in a simulated interaction with an unknown male (B) outside the territorial boundary of the focal males. In response to subsequent intrusion by the second male (B), focal males showed low song output in response to males that had lost to a male that the subject was able to beat. Males of known high quality, or those about which information was ambiguous, elicited a high level of song output by focal males. We discuss the implications of this finding for the evolution of communication and social behaviour.

Abstract: The Sir Philip Sidney game has been used by numerous authors to show how signal cost can facilitate honest signaling among relatives. Here, we demonstrate that, in this game, honest cost-free signals are possible as well, under very general conditions. Moreover, these cost-free signals are better for all participants than the previously explored alternatives. Recent empirical evidence suggests that begging is energetically inexpensive for nestling birds; this finding led some researchers to question the applicability of the costly signaling framework to nestling begging. Our results show that cost-free or inexpensive signals, as observed empirically, fall within the framework of signaling theory.

Abstract: Humans regularly produce new utterances that are understood by other members of the same language community. Linguistic theories account for this ability through the use of syntactic rules (or generative grammars) that describe the acceptable structure of utterances. The recursive, hierarchical embedding of language units (for example, words or phrases within shorter sentences) that is part of the ability to construct new utterances minimally requires a 'context-free' grammar that is more complex than the 'finite-state' grammars thought sufficient to specify the structure of all non-human communication signals. Recent hypotheses make the central claim that the capacity for syntactic recursion forms the computational core of a uniquely human language faculty. Here we show that European starlings (Sturnus vulgaris) accurately recognize acoustic patterns defined by a recursive, self-embedding, context-free grammar. They are also able to classify new patterns defined by the grammar and reliably exclude agrammatical patterns. Thus, the capacity to classify sequences from recursive, centre-embedded grammars is not uniquely human. This finding opens a new range of complex syntactic processing mechanisms to physiological investigation.

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