topLeft

Experiments

topLeft displays a text overlay in the top-left corner of the display screen for the duration of a trial. Typical uses are per-trial status text such as a trial counter, block name, or running score (dynamic %...% variables are supported). It is display-only: it is never read as a response option or spatial target. It is rendered on all main trial types: single-screen image trials, single-screen word trials, and multi-screen trials, where it is shown once at trial start.

Syntax

Type the text you want in the top-left corner, for example Block 1: practice.

Any free text is accepted, and HTML markup in the cell is rendered as markup, so you can style the overlay.

Dynamic variables are substituted before the text is shown: %response%, %rt%, %correct%, %responseCode%, indexed and aggregated forms such as %correct.perc[1,5]%, participant details such as %id%, and your own user variables. Because the overlay is drawn at the start of the trial, these values refer to trials already completed, not to the current one.

Options

Value	Effect
any non-empty text/HTML	Shown top-left for the trial; %...% variables substituted first
text containing %var%	Variable-substituted before display; text without % is shown unchanged
empty cell	Nothing displayed; the corner stays empty

There are no keywords: any value you enter is treated as text.

Defaults & missing values

Leave the column out of the trial file, or leave a cell empty, and nothing is displayed in the top-left corner for that trial.

Column headers are matched case-insensitively, so topleft works too.

Works with

• test set to CFPT: these trials show a built-in trial counter in the top-left corner. Filling in topLeft replaces that counter with your own text.
• topRight: the matching overlay for the opposite corner.
• Multi-screen trials: the text is drawn once at the start of the trial and stays visible across all screens of that trial. It does not change between screens.
• The overlay disappears when the trial ends.
• timer: a trial timer positioned topleft is drawn separately from this column, but in the same corner, so the two can overlap. Put the timer elsewhere if you also use topLeft text.
• The overlay is left-aligned near the top of the display at a fixed size; you cannot reposition or resize it from the trial file.

Examples

Static label:

test	stim1	key	topLeft
learn	apple		Block 1: practice

Running accuracy from previous trials using dynamic variables:

test	stim1	key	topLeft
recognition	face_01	f	Correct so far: %correct.perc[1	0]%

HTML styling:

test	stim1	key	topLeft
recognition	word_a	j	<span style='color:red'>REMEMBER</span>

Tips & gotchas

Caution

The text is drawn before the participant responds, so %...% variables can only report trials that are already finished. Referencing the current trial’s own response or reaction time here never works; use feedback for that.

• This is display-only text. It is never a response option or a click target, no matter what it says.
• On CFPT trials, leaving topLeft empty keeps the built-in trial counter in that corner; filling it in replaces the counter.
• Cell text is treated as HTML, so a stray < or > can swallow part of your label. Escape them if you need the literal characters.

Note

The overlay is not re-drawn between the screens of a multi-screen trial: it shows the same text for the whole trial.

Common combinations

topLeft appears in these worked recipes:

• Running score display: Keep a points tally in the corner of the screen that updates after every scored trial.