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Global-Local Test

Big letters made of small letters. Name the big one, then the small ones, and see how much faster you see the whole than its parts.

Type
Perception
Takes
about 2 min
Result in
milliseconds

Global-Local

~2 min

  1. Each figure is a big letter made of small letters: H or S.
  2. In one half you name the big letter, in the other the small ones. Press H or S, or tap the buttons.
  3. 48 figures. Answer as fast as you can without slipping.

Your result: — ms

How it's measured

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How does the Global-Local Test work?

Each figure is a big letter, H or S, drawn with small letters, also H or S. In one half of the test you name the big letter; in the other half you name the small ones. Answer with the H and S keys or the two buttons, as fast as you can without slipping. A screen before each half says which level to name.

There are 48 figures, 24 in each half, and which half comes first is random. A cross shows for 500 ms before each figure, and no answer within 2.5 seconds counts as a miss. The four figures come equally often:

FigureBig letterSmall lettersThe two levels
H of H'sHHAgree
H of S'sHSDisagree
S of H'sSHDisagree
S of S'sSSAgree

How is the Global-Local Test scored?

Your result is your global advantage: your average time naming the small letters minus your average time naming the big one, right answers only. A positive number means you saw the whole before its parts. Each figure is timed from the animation frame that draws it to the moment your key or finger goes down.

The result also shows interference both ways. When the levels disagree, does the big letter slow you down naming the small ones? And do the small letters slow you down naming the big one? The classic finding is that the first is larger.

What is global precedence in the Global-Local Test?

It is the idea that you see the forest before the trees. David Navon (1977), in “Forest before trees”, used big letters made of small ones and found the big letter was recognized faster, and that it got in the way of naming the small letters more than they got in the way of naming it. Figures like these are still called Navon figures.

What can affect your Global-Local result?

The size of the figure on your screen and how far away you sit: the bigger the figure looks, the more the small letters stand out, so compare runs on the same device. Practice matters too, which is why the order of the two halves is random. Some people simply lean toward detail, and their number comes out small or negative. To find a shape hidden inside a bigger one, try Hidden Figures; to see the whole fool the parts, the Optical Illusion Test.

Questions

Is the Global-Local Test the Navon task?
It uses the same kind of figure Navon used in 1977, big letters made of small ones, and the same comparison of naming the two levels. It is a recreational version with its own letters and timings, and it gives no diagnosis.
What does a negative global advantage mean?
That you named the small letters faster than the big one this time: you went for the detail. It happens, especially on a small screen, where the small letters are easier to make out.
Why does the order of the two halves change?
Because you get faster with practice. If the big letters always came first, the second half would always look easier.
Does screen size matter in the Global-Local Test?
Yes. How big the figure looks changes how easy each level is to see, so compare your results on the same device.