  Graphical perception studies are a key element of visualization research,
forming the basis of design recommendations and contributing to our
understanding of how people make sense of visualizations. However, graphical
perception studies typically include only brief training sessions, and the
impact of longer and more in-depth feedback remains unclear. In this paper, we
explore the design and evaluation of feedback for graphical perception tasks,
called VisQuiz. Using a quiz-like metaphor, we design feedback for a typical
visualization comparison experiment, showing participants their answer
alongside the correct answer in an animated sequence in each trial. We extend
this quiz metaphor to include summary feedback after each stage of the
experiment, providing additional moments for participants to reflect on their
performance. To evaluate VisQuiz, we conduct a between-subjects experiment,
including three stages of 40 trials each with a control condition that included
only summary feedback. Results from n = 80 participants show that once
participants started receiving trial feedback (Stage 2) they performed
significantly better with bubble charts than those in the control condition.
This effect carried over when feedback was removed (Stage 3). Results also
suggest an overall trend of improved performance due to feedback. We discuss
these findings in the context of other visualization literacy efforts, and
possible future work at the intersection of visualization, feedback, and
learning. Experiment data and analysis scripts are available at the following
repository https://osf.io/jys5d/
