Object-based curve tracing in the upper and lower visual fields

L. N Hecht; S. P Vecera

doi:10.1167/5.8.1030

Observers can use attention to trace along a visible path. This curve tracing operator requires more time to trace longer paths (e.g., Jolicoeur et al., 1986; Roelfsema et al., 1999), suggesting an analog-like index of attention. Grouped array accounts of object-based attention would suggest that perceptual grouping cues (e.g., good continuation) influence the allocation of spatial attention in curve tracing tasks. One prediction of the grouped array account is that factors affecting spatial attention should also affect object-based attention. Recent research has shown that spatial attention has different resolutions in the upper and lower visual fields (He et al., 1996). We asked if object-based curve tracing exhibited a similar attentional resolution difference and hypothesized tracing into the lower visual field (LVF) would be faster than tracing into the upper visual field (UVF).Observers viewed pairs of curves, which crossed one another (0–2 times) as they went into the LVF or UVF. Observers were instructed to report which curve's end was connected to the fixation (e.g., Roelfsema et al., 1999). In Experiment 1, the curves were presented until participants responded and eye movements were monitored. Tracing into the LVF was faster than tracing into the UVF. In Experiment 2, curves were only presented for 200 ms. The error data replicated the reaction time data in Experiment 1. In Experiment 3, we examined if these field differences were due to attentional resolution. The two curves were colored differently, thus providing a featural difference between the curves and minimizing the need for focal attention. The differences between the LVF and UVF were reduced, suggesting object-based resolution differences between the fields. The results of these experiments suggest that the attentional resolution differences in the LVF and UVF impact the curve tracing operation, demonstrating the close relationship between space-based and object-based attention.

Object-based curve tracing in the upper and lower visual fields

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