Costs and benefits of voluntary attention in crows.

Behavioural signatures of voluntary, endogenous selective attention have been found in both mammals and birds, but the relationship between performance benefits at attended and costs at unattended locations remains unclear. We trained two carrion crows (Corvus corone) on a Posner-like spatial cueing task with dissociated cue and target locations, using both highly predictive and neutral central cues to compare reaction time (RT) and detection accuracy for validly, invalidly and neutrally cued targets. We found robust RT effects of predictive cueing at varying stimulus-onset asynchronies (SOA) that resulted from both advantages at cued locations and costs at un-cued locations. Both crows showed cueing effects around 15-25 ms with an early onset at 100 ms SOA, comparable to macaques. Our results provide a direct assessment of costs and benefits of voluntary attention in a bird species. They show that crows are able to guide spatial attention using associative cues, and that the processing advantage at attended locations impairs performance at unattended locations.

Exogenous and endogenous spatial attention in crows.

Attention describes the ability to selectively process a particular aspect of the environment at the expense of others. Despite the significance of selective processing, the types and scopes of attentional mechanisms in nonprimate species remain underexplored. We trained four carrion crows in Posner spatial cueing tasks using two separate protocols where the attention-capturing cues are shown at different times before target onset at either the same or a different location as the impending target. To probe automatic bottom-up, or exogenous, attention, two naïve crows were tested with a cue that had no predictive value concerning the location of the subsequent target. To examine volitional top-down, or endogenous, attention, the other two crows were tested with the previously learned cues that predicted the impending target location. Comparing the performance for valid (cue and target at same location) and invalid (cue and target at opposing locations) cues in the nonpredictive cue condition showed a transient, mild reaction time advantage signifying exogenous attention. In contrast, there was a strong and long-lasting performance advantage for the valid conditions with predictive cues indicating endogenous attention. Together, these results demonstrate that crows possess two different attention mechanisms (exogenous and endogenous). These findings signify that crows possess a substantial attentional capacity and robust cognitive control over attention allocation.