I recall a visual search task where participants would search for a single item with either one or two distinct features. For example one would look for an X in a set of Os as "one feature" or instead they would look for a red X in a set of red Os, blue Os and blue Xes. The results indicated it was significantly harder to locate an item with two distinct features (a red X) while finding a single feature (an X) was almost instantaneous.

I'm sure I could find the studies on my own but I don't know the name of the search task. I recently saw a simplistic version on Facebook (this is not from a specific published article):

Search Task Example

This version is the same basic idea of the single feature search. What's the name of this sort of visual search for distinct features?


2 Answers 2


Aren't you just looking for a conjunction search task?

Normally it works like this: objects are described in terms of their features (e.g., colour, shape, etc.). If you tell people to search for a target with a given colour AND shape, then this is a conjunction of features, and is termed a conjunction task.

Note that there are complex dynamics in terms of how this works, and the second link below discusses this at length.

Here's some links on this type of thing:



Here are examples of Feature Search vs Conjunction Search from Wikipedia:
Feature Search:

enter image description here

Conjunction search:

enter image description here

  • 2
    $\begingroup$ Yes! That's exactly it, the images in the Wikipedia article are exactly what I recall. en.wikipedia.org/wiki/Visual_search#Feature_search Feature search is also relevant though; I was specifically thinking about how Feature search is faster than Conjunction but couldn't remember the search types. $\endgroup$
    – Ben Brocka
    May 30, 2012 at 16:06
  • 1
    $\begingroup$ Great! Good call on adding the examples also. It's also worth noting that some studies have shown that not all features are equal. For example, colour is very good at guiding attention; shape less so. See: mendeley.com/research/… $\endgroup$
    – vizzero
    May 30, 2012 at 18:47

This might not be exactly what you're after, but Ackerman, Beier, and Boyle (2002) wrote a paper where they factor analysed various perceptual speed tests along with other tests. In particlar, the test you are interested in seems to be a member of the sublass of perceptual speed tests that Ackerman et al labelled "Perceptual Speed: Pattern Recognition".

They used the following tests to measure the factor.

  1. Finding a and t. In this test, participants scan for instances of “a” and “t” in text passages (passages were in Italian).
  2. Mirror Reading. In this test, participants find target words written in mirrored text.
  3. Summing to 10. In this test, participants circle pairs of numbers if they sum to 10.
  4. Finding and ¥. This test is the same as Finding a and t, except the text was random symbols.
  5. Canceling Symbols. In this test, participants scan a page for a single target figure among other simple target figures.

However, these tests were typically designed for paper and pencil administration and for measuring individual differences. I don't think they used the one-symbol for each trial approach. In particular, I remember a colleague using the Finding A's test in the Ekstrom battery.


  • Ackerman, P.L. and Beier, M.E. and Boyle, M.D. (2002). Individual differences in working memory within a nomological network of cognitive and perceptual speed abilities. Journal of Experimental Psychology: General, 131, 4, 567. PDF
  • Ekstrom, R. B., French, J. W., & Harman, H. H. (1976). Manual for kit o f factor-referenced cognitive tests. Princeton, NJ: Educational Test- ing Service.

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