Human-Computer Interaction Lab, University of Maryland, College Park, MD 20742, USA. csparr@umd.edu|Human-Computer Interaction Lab, University of Maryland, College Park, MD 20742, USA. csparr@umd.edu|Human-Computer Interaction Lab, University of Maryland, College Park, MD 20742, USA. csparr@umd.edu|Human-Computer Interaction Lab, University of Maryland, College Park, MD 20742, USA. csparr@umd.edu