ABSTRACT
Attention is defined as the ability to process selectively one aspect of the environment over others and is at the core of all cognitive processes such as learning, memorization, and categorization. Thus, evaluating and comparing attentional characteristics between individuals and according to situations is an important aspect of cognitive studies. Recent studies showed the interest of analyzing spontaneous attention in standardized situations, but data are still scarce, especially for songbirds. The present study adapted three tests of attention (towards visual non-social, visual social, and auditory stimuli) as tools for future comparative research in the European starling (Sturnus vulgaris), a species that is well known to present individual variations in social learning or engagement. Our results reveal that attentional characteristics (glances versus gazes) vary according to the stimulus broadcasted: more gazes towards unusual visual stimuli and species-specific auditory stimuli and more glances towards species-specific visual stimuli and hetero-specific auditory stimuli. This study revealing individual variations shows that these tests constitute a very useful and easy-to-use tool for evaluating spontaneous individual attentional characteristics and their modulation by a variety of factors. Our results also indicate that attentional skills are not a uniform concept and depend upon the modality and the stimulus type.
ABSTRACT
Stimuli such as visual representations of raptors, snakes, or humans are generally assumed to be universally fear-inducing in birds and considered as a product of evolutionary perceptual bias. Both naïve and experienced birds should thus react to such stimuli with fear reactions. However, studies on different species have shown the importance of experience in the development of these fear reactions. We hypothesized that the responses of adult European starlings to fear-inducing visual stimuli may differ according to experience. We compared the reactions of Hand-raised adults with no experience of predators to those of Wild-caught adults, with potentially extensive experience with predators. Three visual stimuli (i.e. human, raptor, snake) were broadcast to 17 birds as 2D pictures (displayed via a LCD screen) with different modalities of presentation: degree of proximity and with or without movement. The results reveal that the birds were particularly sensitive to proximity and movement, with more attention towards moving stimuli and more withdrawal for close stimuli. The human stimulus elicited attention in both the distant and moving modalities but, like the other stimuli, mostly withdrawal when it was close. Developmental experience appeared to influence the emotional level, as the Hand-raised birds reacted strongly to all stimuli and all modalities, contrarily to the WC birds which performed withdrawals almost only for close stimuli and attention to moving stimuli. Stimuli proximity and movement seemed, therefore, relevant features that elicited negative reactions in Wild-caught birds. The Hand-raised birds were equally attentive to both distant and moving stimuli. Thus the young birds showed no real discrimination. Early and later experiences may, therefore, influence birds' reactions. Starlings may require experience with real threats to develop adaptive responses, i.e. limiting unnecessary loss of energy by fleeing in front of non-dangerous stimuli.
