First, download & print the cards from here. I laminated mine to keep them as long as possible but that really is completely optional. We look at each card and identify what senses we would use to perceive the item on the card. Then, using a small clip (I like these), my kids have to put the clip over the correct sense.
Now if you notice, some of these cards have various answers, which is exactly how we perceive things in real life. When our senses are coded in the brain they do so through numerous avenues, so I designed these cards to mirror that. Sorry, but you just can't take the neuroscientist out of me ;-) So with a trash truck, you would put a clip over the eye because you can see it, but you could also put one on the ear because you can also hear it. To start off with I would just do one at a time, but as the child progresses you can introduce the idea that multiple senses are used simultaneously.
We really like this activity because we can talk about our sense for units on health, the letter 's', and this can grow with a child's cognitive development. Check these out and tell me what your preschooler thinks :-)
What tasks do you use with YOUR preschooler to learn their senses?