AbilityBenchShepard-Metzler-style figures, angle by angle
Mental rotation test that plots your response time against angle
Two block figures appear side by side and you say whether they are the same object turned or a mirror image no rotation can bring together. The angle between them is set to 0, 40, 80, 120 or 160 degrees, so the run can draw your response time against angle, fit a straight line and report its slope in milliseconds per degree. The average time is mostly seeing and pressing a key; the slope is the part that is rotation.
Two cube figures, side by side. The one on the right has been turned about its vertical axis by 0, 40, 80, 120 or 160 degrees — and on half the trials it was reflected first, so no amount of turning will ever bring it into line. Decide which, 50 times, and the run fits a straight line through your times.
The run, in full
- Figures
- 10 or 11 cubes in three straight runs meeting at right angles
- Turn
- 0, 40, 80, 120, 160 degrees about the figure's own vertical axis, in depth
- Half the trials
- the comparison is reflected first, and no turn will ever match it
- Keys
- S = same object, L = mirror image
- Trials
- 50 scored — 5 at each turn in each answer, one break after 25
- Window
- 15 seconds per pair, which is long because rotating 160 degrees is not fast
- Fitted on
- correct same-pair trials only, after a 3-MAD outlier rule
Practice pairs have no clock on them at all and name the right answer afterwards. They are excluded from the fit, from the accuracy figure and from the chart.
What Shepard and Metzler found
The 1971 experiment is famous for a chart rather than a score. Participants judged pairs of block figures, and their response times rose almost perfectly linearly with the angle between the two, right up to 180 degrees. That straight line is the argument: if people were matching features or checking a stored description, there is no reason time should track angle at all, and a continuous turn of an imagined object is the simplest thing that produces it. The rate the line implies is ≈ 17 ms per degree — Shepard & Metzler (1971), Mental rotation of three-dimensional objects, Science — and this page prints it beside your own slope as an order of magnitude, never as a rank. It comes from a few practiced participants in a laboratory; yours comes from a keyboard nobody calibrated, so the comparison that holds is you against you, a week apart on the same machine.
How the slope is measured
| Trials | 50 scored — five angles by two pair types, five of each — after six practice pairs that tell you whether the key was right and reach no figure. A rest at trial 25 lasts as long as you want |
|---|---|
| Angles | 0, 40, 80, 120 and 160 degrees about the figure's own vertical axis. In depth rather than in the plane of the screen, because a flat drawing turned in the plane can be matched by tilting your head |
| Mirror pairs | Half the trials. They are answered and counted for accuracy, and left out of the line: a mirror trial ends when you stop searching, and the moment somebody gives up is not a rotation time |
| One trial | A 400 ms fixation cross, a gap drawn between 250 and 650 ms so the onset cannot be anticipated, then the pair until you answer or 15 seconds pass |
| The fit | Least squares through correct same-pair trials, after a median-based rule removes trials where attention left the screen. The slope, the intercept and the variance explained are printed, and the dropped trials are counted |
A reaction time here is the interval between the frame that painted the stimulus and the timestamp the browser attached to your key, both read from the same monotonic clock. What neither can see is the display pipeline behind it, so on a 60 Hz screen roughly 16 ms of every figure below is the machine rather than you. That is the timing floor: two numbers closer together than that are the same number, and this page reports no precision it cannot support.
For a slope the floor is unusually benign. A constant delay between the frame and your finger is added to every trial whatever the angle, so it lifts the whole line and leaves its steepness alone — the intercept absorbs it, which is why the intercept is printed and not interpreted.
Reading your line
What does a slope of 17 milliseconds per degree mean?
That every extra degree between the two figures cost you about another 17 thousandths of a second — a turning speed of roughly 60 degrees a second, so 180 degrees of separation adds about three seconds on top of whatever every trial costs anyway. Your average response time is dominated by seeing the figures, deciding and pressing a key, which are the same on every trial and say nothing about rotation; the slope is what changes with angle.
My line is nearly flat. Did I do something wrong?
Look at the scatter before concluding anything. A flat line with tight dots means the angle genuinely cost you little. A flat line with dots sprayed everywhere means the fit had nothing to hold on to, and the variance explained printed beside the slope will be small — that run is one to repeat rather than interpret. A third possibility is a strategy that is not rotation at all: matching a distinctive feature such as the end cube and answering without turning anything produces a flat line by construction.
Is it true that men score higher on mental rotation?
A group difference of 0.5-0.9 Cohen's d is reported (Voyer, Voyer & Bryden (1995), Magnitude of sex differences in spatial abilities: a meta-analysis and consideration of critical variables, Psychological Bulletin), and it is why this test attracts the claim. It says nothing about you: at that size the two distributions overlap across most of their range, and the difference moves with the test used, with whether guessing is penalized and with practice. This page reports your slope and your accuracy and places you in no group.
Rotation is narrower than it feels
Being fast here predicts less than people expect about the rest of spatial ability. Imagining a sheet folding is a different operation, measured on the paper folding test, and the spatial reasoning test samples turning, folding and cutting side by side. If the cube figures look flat or effortful to you, the stereopsis test checks whether depth is reaching you from both eyes before you read anything into a spatial score.
This is a measurement exercise, not a clinical assessment. It reports what you did on this page against a stated reference and nothing more — it cannot establish a spatial deficit, dyspraxia or anything neurological. Only a qualified professional, working with more than a browser, can make that judgment.