Here are three "observational" tests I give my students when I start talking about the importance of making good observations in science.
The first picture students have to find the arrow on the FedEx truck. I give them 2 minutes.
The second they have to find the hidden tiger.
The third they have to count how many "F's" are in the sentence. That is a fun one because they have a minute to count them and they all secretly write down their number and then I have them read them out loud and rarely does anyone get the same number.
The kids love being fooled. For the answers check the comments section.