Appropriate grades or age groups:
Grade 4 and up.

Estimated time to complete this project:
Variable; we did it in a sort of patchy manner, over the course of a month. The science fair guidelines suggested/required validation by repetition, so each phase of it was essentially repeated 5 times! Verrry happy cats...

Materials:
several varieties of dried catnip herb from pet store and grocery store, plus a spray bottle of catnip stuff

one live catnip plant

cats! preferably, your own felines...

towels to lay on the carpet

3 or 4 reference books/internet sources for reporting of data concerning catnip and its effects on cats

Instructions:
We made a trip to the grocery store and purchased the low-end variety of catnip, which is powdery and has more stem than leaf, and little if any blossom material. We went to the pet store and purchased a live catnip plant plus several varieties of the dried herb, which can be every bit as pricey as the herbs we use in the kitchen.

Cost was part of the data put in the science fair notebook, as basis for why to explore the differences. This sixth grade class is very much into computers, so findings have bar graphs and pie charts that were lacking in previous years.

The observer places a towel on the floor and sprinkles some catnip on it, then invites the kitties to give their opinions. All manner of cat body language and behaviors are noted and compared. Cats eat it, roll in it, sneeze, purr, search for a different kind if they don't like what's on the towel, etc. These behaviors were also neatly charted, vs. being scribbled in a wire-bound notebook and re-copied by hand for neatness (charming in primary grades, frowned upon by 6th if computers are available during class time).

Other comments or suggestions:
Experiments involving "verebrates" often involve seeking permission from the school science fair coordinator. This is to assure that animals will not be abused in any manner.

Leave the non-scientist kids at home while you shop! The "Mom, can we have another kitty/puppy/fish?" questions will wear you down, and you may spent too much and get more or less than needed for the experiment. Likewise, having small brothers and sisters enter the room during the Great Experiments tends to frighten the cat, disrupt the experiment, and enrage the jr. scientist sibling.

Our particular cats indicated to us that two varieties of the dry herb sold at the petshop were just as desirable (if not more so) than the fresh plant material. One reason for this, though, is that the plants available in winter and early spring lack blossoms! To explain away this problem, we cited years of observing the cats enjoy the more mature flowered plants, which is surely true. We learned that in the 'off-season' we can save time, money, gasoline, etc., by relying on the dry catnip, and the finicky felines will actually be happier that way. (As if we were bowing to their every whim anyway; we got a little desperate for Topic this year!) Regarding the spray, the non-aerosol brand we bought this time was gross; we have had an aerosol spray in the past which was not obnoxious, and the cats seemed to enjoy it.

I should note that some cats do not like, or completely ignore, catnip. Very old and very young cats in particular may not have an affinity for the stuff. Others will nibble live plants down to a nub, and curl up in the flower pot for a snooze. In summer, we suspend our catnip plants (3 or 4 small ones) in a large hanging macrame pot sling. The purchased experiment materials only made it beyond day 1 because we kept them in one shopping bag, suspended from a hook in the bathroom, where the cats would have had to leap like Tarzan to get to it. I have seen mine bite holes into plastic tubs and lids.

The project rated an A+ for the classroom presentation; the actual science fair happens a week later. Initially I was not thrilled with having a week less to work with, but the blessing is, it forces this naturally procrastinating age group to wrap up and finish in a timely manner.