Testing between the gunpowder fuse and the filling-hose analogy for mental curve tracing using electroencephalography: boom!

Curve tracing occurs when a line is followed covertly to accomplish a task, for example, to determine whether two landmarks are on the same line or not (could Highway 61 take Robert Johnson from New Orleans to St Louis?). Previous work suggests that attention either moves along the curve, momentarily activating local representations of the curve during this process, leaving little or no trace of this activation once attention has passed, or attention spreads along the curve, resulting in an activated state along the entire portion of the curve that was traced. We re-examined this issue using event-related potentials. Curves to be traced were presented briefly to encourage a rapid deployment of attention. The curves started on the vertical midline and passed into the left or right visual field and terminated either on the vertical midline or at a lateral position. We measured a posterior contralateral negativity (relative to the visual field of the traced curve) that offset more rapidly when the curve was traced back to the midline than when it remained lateral. The results suggest that attention travels along the curve like fire on a fuse, with activation returning to baseline once the flame has passed.