Provide students with a list of animals of different types -- mammals, reptiles, amphibians, fish and birds. Then, provide a list of questions they can answer about each animal, such as: Does it have fur? Does it lay eggs or give birth to live young? Does it have feathers? Does it have gills? Students can use their existing knowledge about animal types to deduce the answers for each animal on their lists. For example, they know all mammals have fur, are warm-blooded and give birth to live young. Because they know that a lion is a mammal, they also know it has fur, is warm-blooded and births live offspring.
Puzzles are another great way to teach deductive reasoning. Geniuspuzzles.com offers an imaginative example that uses the food chain as the context: (Consider first that the following animals mentioned are smart enough to apply reason themselves.) "There are six leopards and one sheep. Leopard[s] can eat sheep, but because the land is magical, the leopards who eat the sheep turn into sheep and then can be eaten by the remaining leopard(s). If we leave them for some time then how many sheep and leopards will be there, when we come back?" Students can deduce that after the first leopard eats a sheep and transforms, the other leopards -- who are smart -- will learn, and refrain, leaving five leopards and one sheep.
Fill-in-the-blank activities can be used to illustrate deductive reasoning in the context of life sciences. Students can use the context of the surrounding information to deduce the word that should go in the blank. For example: The gas helium is stable, and stable gases are noble; therefore, helium is ______. Students can follow the logic of the passage to deduce that helium is a noble gas.
Hangman is another deductive reasoning-based game. It also keeps lessons fun. One player, called the executioner, chooses a word based upon an agreed theme (chemistry, in this case) and on a sheet of paper draws an underscore for each letter of the word. Each other player then use the theme, or hint, in addition to all previously guessed letters to deduce each remaining missing letters, and then finally the word itself. For each incorrect guess, the executioner draws one piece of the hangman. If a player guesses the word before the drawing of the hangman is complete, that player wins. If not, the executioner wins.