Trial-by-trial feedback fails to improve the consideration of acceleration in visual time-to-collision estimation.

When judging the time-to-collision (TTC) of visually presented accelerating vehicles, untrained observers do not adequately account for acceleration (second-order information). Instead, their estimations only rely on vehicle distance and velocity (first-order information). As a result, they systemically overestimate the TTC for accelerating objects, which represents a potential risk for pedestrians in traffic situations because it might trigger unsafe road-crossing behavior. Can training help reduce these estimation errors? In this study, we tested whether training with trial-by-trial feedback about the signed deviation of the estimated from the actual TTC can improve TTC estimation accuracy for accelerating vehicles. Using a prediction-motion paradigm, we measured the estimated TTCs of twenty participants for constant-velocity and accelerated vehicle approaches, from a pedestrian's perspective in a VR traffic simulation. The experiment included three blocks, of which only the second block provided trial-by-trial feedback about the TTC estimation accuracy. Participants adjusted their estimations during and after the feedback, but they failed to differentiate between accelerated and constant-velocity approaches. Thus, the feedback did not help them account for acceleration. The results suggest that a safety training program based on trial-by-trial feedback is not a promising countermeasure against pedestrians' erroneous TTC estimation for accelerating objects.

Directional nanotopographic gradients: a high-throughput screening platform for cell contact guidance.

A novel approach was developed using PDMS-substrates with surface-aligned nanotopography gradients, varying unidirectional in amplitude and wavelength, for studying cell behavior with regard to adhesion and alignment. The gradients target more surface feature parameters simultaneously and provide more information with fewer experiments and are therefore vastly superior with respect to individual topography substrates. Cellular adhesion experiments on non-gradient aligned nanowrinkled surfaces displayed a linear relationship of osteoblast cell adhesion with respect to topography aspect ratio. Additionally, an aspect ratio of 0.25 was found to be most efficient for cell alignment. Modification of the surface preparation method allowed us to develop an approach for creating surface nanotopography gradients which innovatively provided a superior data collection with fewer experiments showing that 1) low amplitude with small wavenumber is best for osteoblast cell adhesion 2) indeed higher aspect ratios are favorable for alignment however only with features between 80-180 nm in amplitude and 450-750 nm in wavelength with a clear transition between adhesion and alignment efficiency and 3) disproved a linear relationship of cell adhesion towards aspect ratio as was found for single feature substrate analysis.