Behavioural variables influence contact call rate more than characteristics of the vegetation in a group-living passerine species.

Although the contact calls of birds have been studied for their acoustic properties, limited research has investigated their repetitive nature. The rate of contact calls could be related to movement, with recruiting birds signalling their location, or it could help maintaining spacing between group mates, or give information about the environment where both signaller and receiver are located. If maintaining spacing, higher call rates would be expected in denser vegetation; alternatively, if birds gain information about predation risk from the cessation of contact calling, then open areas might elicit higher call rate. We studied how contact call rate in groups of Swinhoe's White-eyes (Zosterops simplex) was influenced by vegetation, collecting a total of 800 recordings. After statistically controlling for group size, the vegetation effect was weak and inconsistent. However, flying individuals produced a distinct flight call consisting of repeated notes similar to contact calls, and group-level contact call rate increased before flights, particularly when birds flew into the group. Therefore, we believe that contact call rate indicates information about individual or group movements, and could function as a continuous signal about the need for recruitment. We encourage further studies investigating how habitat, risk and audience influence contact call rate.

Spontaneous gesture and spatial language: Evidence from focal brain injury.

People often use spontaneous gestures when communicating spatial information. We investigated focal brain-injured individuals to test the hypotheses that (1) naming motion event components of manner-path (represented by verbs-prepositions in English) are impaired selectively, (2) gestures compensate for impaired naming. Patients with left or right hemisphere damage (LHD or RHD) and elderly control participants were asked to describe motion events (e.g., running across) depicted in brief videos. Damage to the left posterior middle frontal gyrus, left inferior frontal gyrus, and left anterior superior temporal gyrus (aSTG) produced impairments in naming paths of motion; lesions to the left caudate and adjacent white matter produced impairments in naming manners of motion. While the frequency of spontaneous gestures were low, lesions to the left aSTG significantly correlated with greater production of path gestures. These suggest that producing prepositions-verbs can be separately impaired and gesture production compensates for naming impairments when damage involves left aSTG.

Naming and gesturing spatial relations: evidence from focal brain-injured individuals.

Spatial language helps us to encode relations between objects and organize our thinking. Little is known about the neural instantiations of spatial language. Using voxel-lesion symptom mapping (VLSM), we tested the hypothesis that focal brain injured patients who had damage to left frontal-parietal peri-Sylvian regions would have difficulty in naming spatial relations between objects. We also investigated the relationship between impaired verbalization of spatial relations and spontaneous gesture production. Patients with left or right hemisphere damage and elderly control participants were asked to name static (e.g., an apple on a book) and dynamic (e.g., a pen moves over a box) locative relations depicted in brief video clips. The correct use of prepositions in each task and gestures that represent the spatial relations were coded. Damage to the left posterior middle frontal gyrus, the left inferior frontal gyrus, and the left anterior superior temporal gyrus were related to impairment in naming spatial relations. Production of spatial gestures negatively correlated with naming accuracy, suggesting that gestures might help or compensate for difficulty with lexical access. Additional analyses suggested that left hemisphere patients who had damage to the left posterior middle frontal gyrus and the left inferior frontal gyrus gestured less than expected, if gestures are used to compensate for impairments in retrieving prepositions.