Treffer: Temporal dynamics of competition in global/local attentional selection.

Attention shifts between global and local levels of visual objects, and these dynamics are altered in neuropsychiatric disorders. However, characterizing such dynamics is difficult because traditional Navon stimuli do not allow for the temporal separation of global and local information. We first investigated whether attentional selection mechanisms used with novel single-level stimuli are shared with those activated by traditional compound figures. In Experiment 1, two sequential target letters (referred to as T1 and T2) were shown at the same or different hierarchical levels with varying stimulus onset asynchronies (SOAs). When both targets were single-level stimuli, T2 recognition-conditional on correct T1 responses-was accurate following same-level transitions but impaired after different-level transitions, especially at short SOAs-an attentional blink (AB) that was stronger for global-to-local than local-to-global switches, replicating previous findings. Using a hybrid design with a traditional Navon T1 (cued to a single level) followed by a single-level T2, the same pattern emerged, indicating transfer of attentional effects across stimulus formats. The AB magnitudes correlated across paradigms, supporting shared mechanisms. To see if the attentional dynamics varied across participants, we applied this hybrid design in Experiment 2 to a larger sample, and used mixture modeling to explore individual differences, revealing four distinct clusters that varied in AB recovery speed depending on switch type, although a continuum of abilities cannot be excluded. These results demonstrate significant variability in attentional dynamics. Single-level stimuli thus offer a powerful tool to disentangle neural responses to hierarchical levels and provide new insights into both typical and disordered attentional processes.
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