I saw this problem on a social network. There are five answers to this question. Four are more or less obvious. The fifth one is enlightening. Here is the analysis:
- #2 is different because it is the only one without a frame
- #3 is different because it is the only circle
- #4 is different because it is the only green shape
- #5 is different because it has a different size
- #1 is different because it is the only shape that belongs to majority in all 4 categories.
So much for patterns and our ability to detect them.