Individual differences in the temporal dynamics of object-based attention

Attention can be focused on specific locations in our visual field (space-based attention), but also spreads along objects (object-based attention). However, space- and object-based effects are prone to large individual differences, and whereas space-based effects are stable, object-based effects are not as prevalent as previously assumed. In the current study, we investigate whether the low prevalence of object-based effects is related to individual differences in the temporal dynamics of attentional selection. We measured space- and object-based effects on reaction times for individual participants in a two-rectangle discrimination task, in which cue-target intervals were varied between 50 and 600 ms. We used bootstrapping to investigate cue-to-target intervals with maximal object-based effects, and fast Fourier transform (FFT) to investigate the rhythmic sampling of visual space within and between objects. Whereas overall, space-based effects were robust and stable across all cue-to-target intervals for most participants, object-based effects were small and were only found for a small subset of participants. In the frequency domain, our results confirm rhythmic patterns of visual-target detection within (8 Hz) and between objects (4 Hz and 8 Hz). However, we found large inter-individual variability in sampling rhythm phases and no consistent phase relationship. Taken together, the low-prevalence of object-based effects cannot be explained by inter-individual variability in the temporal dynamics of attentional selection. Our results provide strong evidence for considering individual variations in developing theories of visual attention