What's the name of this visual search task? 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):



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?
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:

http://www.mendeley.com/research/guided-search-an-alternative-to-the-feature-integration-model-for-visual-search/

http://www.mendeley.com/research/visual-search-stimulus-similarity-2/

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



Conjunction search: