Accessibility Statement

This statement applies to the web application Classperiment, a teaching tool for classroom experiments in cognitive psychology.

The platform chrome — joining a session, consent, task instructions, results, rankings, and the instructor screens — targets conformance with WCAG 2.1 Level AA, as required by BITV 2.0 and EN 301 549.

The speeded visual reaction-time paradigms (for example Stroop, Flanker, and visual search) are measurement instruments, not informational content. The constructs they measure are inherently dependent on vision and reaction time: presenting their stimuli through a screen reader or removing the time pressure would destroy the very phenomenon each task is designed to demonstrate. These task runners are therefore exempt from the conformance target above.

Within that constraint, the tasks are built accessibility-first where the science allows it: 68 of 75 task runners are fully keyboard-operable (no pointer required on desktop), and non-essential animation respects the reduced-motion preference of your operating system.

The task Mark the Middle asks you to mark the middle of horizontal lines with one click or tap; the marking needs a mouse, a touchpad, a pen or a touchscreen, because the free position of the press is what is measured. The instructions, the Ready button, the screens and the results work with the keyboard, and the start screen, the screen before the 24 lines and every pause screen offer to skip the task.

The task Discover a ranking shows two invented names on two cards and asks which of them ranks higher, within 4 seconds per pair; learning the order from the feedback under this time limit is the task itself. You answer with the keys F (left card) and J (right card) or by tapping or clicking a card; the feedback and the counters are announced to screen readers, and the higher name is marked by a border and a symbol as well as by colour. The instructions, the screens between the phases, the end dialog and the results work with the keyboard and screen readers, and “End task” can be reached with the Tab key on every screen up to the end of the test.

The task Letters at a Glance shows a field of twelve letters for about 50 milliseconds and then an arrow that marks one row; seeing the brief field is the task itself, so the letters are not read out to screen readers. The instructions, the examples, the screens between the blocks and the results work with the keyboard and screen readers; the four letters of the row are entered by typing them (? stands for “Don’t know”, Backspace deletes, Enter confirms) or on an on-screen letter pad with keys of at least 44 × 44 pixels, within 8 seconds per row (the positions set by then count). “Skip task” is offered on the start screen, before the practice and the main part, in the breaks between the blocks and on every screen after an interruption (“Skip today” at the display check). Changing the window size or the zoom before the arrow has ended, or hiding the page before the answer has ended, makes that trial invalid; below 50 frames per second the task does not start a block.

The task Recognising Words shows two short lists of German words one at a time and then asks for single words whether they were in the lists; reading the words in their fixed rhythm is the task itself, so they are not read out to screen readers during the lists. The instructions, the screens between the parts and the results work with the keyboard and screen readers, the answers with the keys F and J or two large buttons (6 seconds per word; instructors can choose a mode with 10 seconds). Hiding the page or switching to another window while the lists are shown ends the run; during a question it makes that question invalid.

The task Judging symbols shows a photo or a grey square very briefly and then an abstract symbol, which you judge as rather pleasant or rather unpleasant; seeing them is the task itself, so the pictures are not described to screen readers. A note before the start names the pictures, and you can skip the task there. The instructions, the questions and the results work with the keyboard and screen readers, the answers with the keys F and J or two large answer fields (5 seconds per symbol). Changing the window size or the zoom, or switching to another window during a trial makes that trial invalid.

The task Spot the Stripes asks you to tell the direction of briefly shown stripes; seeing them is the task itself, so a spoken description of the pattern would change what is measured. The instructions and the results work with the keyboard and screen readers, the answers with the keys F and J or two large buttons (1.8 seconds per answer), and every screen of the task lets you skip it. Changing the window size or the zoom while a pattern is shown makes that trial invalid.

The task Colours in Memory asks you to remember colours and to choose one again on a colour wheel; telling colours apart is part of the task, and its first screen lets you skip it (nothing is asked about your colour vision). The wheel works with the mouse, by touch or with the keyboard (the arrow keys choose, Enter confirms), within 8 seconds per answer; no numbers or colour names are shown, and screen readers hear only whether a colour has been chosen. Changing the window size or the zoom during a trial makes that trial invalid; you can enlarge the page before you start.

The card sorting task is not speeded: you take as long as you need for each card. It is still a measurement instrument, for two reasons. First, colour is one of the three properties the cards are sorted by, so it cannot be replaced by another cue; the four colours were chosen to stay distinguishable with common colour-vision deficiencies and also differ in lightness, and every figure has a dark outline. Second, the instructor sets a time limit per card (5 to 30 seconds, 15 by default). It pauses while the page is in the background. Running into it brings up the next card and is not counted as an error, but it restarts the count of correct sorts in a row. The cards can be sorted with the keys 1 to 4 or with Tab and Enter, and screen readers receive each card as a text description.

If you encounter a barrier while using Classperiment, or need any content in an accessible format, please contact:

Dr. Marian Sauter, marian.sauter@uni-ulm.de, +49 (0)731 50 31155.

This statement was prepared on July 12, 2026, based on a self-assessment of the application. A formal accessibility audit is planned for November 2026; this statement will be updated with its results.