Generality. The generality should only include things which help the learner to classify. When we want the learner to learn other things about the concept, a different type of learning is involvedóunderstanding. However, it is helpful to understand that some concepts are defined on the basis of critical characteristics, whereas others are defined on the basis of functions. These are called criterial definitions and functional definitions, respectively. For example, "chair" can be defined as something to sit in with back support, or it can be defined as having a seat, raised off the ground, and a back. A definition can also have bothcriterial and functional tactics. For example, a chair is something to sit in, and it has a back. 

Examples. Given the purpose of presenting examples as discussed above, we should make sure they are very divergent (as different as possible from each other), and we should present some of them with matched nonexamples. Markle and Tiemann (1969) have identified what they call a "minimum critical subset" of examples, which is one of each of the major types of examples that comprise the concept class. This means that in designing the examples, you must first identify all the major ways that the examples can differ. 

Practice. Since the learners need to be able to generalize the classification skill to examples that they have never seen before, your practice should always present new instances (ones not used in the examples), and they should be divergent from each other, including at least one "minimum critical subset" of instances. 

Feedback. If learners practice the wrong responses without being corrected, those wrong responses are likely to become difficult to change. Thus, it is very important to correct wrong responses as soon as possible after they occur. This is called "informational feedback." If the learners get it right, you can confirm their response. If they get it wrong, you can give them the correct response with explanations or give them hints that help them to figure out how to correct their own responses. But feedback can serve a second purposeómotivationówhich is discussed in the next section. 

Does this mean that your sequence of routine tactics should be generality-example-practice? Certainly not. We have seen that the instruction should begin with prototype formation. Hence, a prototypical example should lead the instruction, usually with a simultaneous presentation of the generality. Also, young learners tend to benefit from plentiful examples before presentation of the generality, and you may want to use a discovery approach where the generality isn't presented at all until it has been discovered. 

Next, it is often helpful for learners to be able to skip around among the instructional tactics. After looking at the generality and prototypical example, a learner might think she already knows the concept. She could then go directly to the more difficult practice to test herself. If she gets it wrong, she could go back and look at an example of medium difficulty, then go and try out a practice item of medium difficulty or take a look at the generality again, and so forth. All that's needed to facilitate such learner control is to clearly label the various routine tactics. This is a more practical and empowering solution to individual differences than designing different instruction for each learner. 
 

Power Tactics

When a concept is difficult for the learners to learn to classify, additional tactics can be used to increase the power of the instruction. It is helpful to think of such instructional enhancement as existing for eachroutine tactic. 

Generality. So how can the generality be srengthened? There are several ways. You can facilitate encoding by focusing the learner's attention on the important parts of it: the label and the critical characteristics. Or you can facilitate encoding by providing a variety of representations of the generality, like a diagram or a paraphrase. You can also present an algorithm (Landa, 1976), a set of steps for the learner to use in checking to see if all of the critical characteristics are present. 

Examples. The most obvious way to enhance this routine tactic is to increase the number of examples. But we can also make it easier to learn from each example. Since examples are different from each other, some are likely to be harder to identify as examples of the concept. The easier examples should be presented first, followed by progressively more difficult ones. This is called an easy-to-difficult sequence. We can also use attention-focusing to relate the example to the generality by pointing out the presence or absence of critical characteristics in the example. And we can use a variety of representations for the examples, to facilitate "dual encoding" of the information. 

Practice. The only ways that practice itself should be enhanced are to increase the number of practice items, to use an easy-to-difficult sequence, and to include prompting on early practice items. Otherwise, ehancements should be reserved for the feedback. 

Feedback. Enhancement on the feedback should be much like on the examples. We can use attention-focusing which relates the instance to the generality by pointing out the presence or absence of critical attributes. And we can use a variety of representations for the correct-answer feedback. Of course, motivational enhancement can also be used:  praise for correct answers and encouragement for wrong answers. 
 

In summary, the following guidelines (or prescriptive principles) are likely to improve the quality of your instruction: 
 

Make sure prerequisites (critical characteristics) have been mastered. 

Present a prototypical example, with explanation. 

Make a generality available. 

Make additional examples available, with explanations. 

Present some of the examples with matched nonexamples. 

Make practice available. 

Provide feedback on all practice (confirmation, explanation, or hint) 

Make instances as different as possible. 

Arrange instances in an easy-to-difficult order. 

Use a variety of representations.
 

Common Errors Novice Designers Make

There are several errors that novice instructional designers commonly make when designing instruction on concept classification tasks. First, they often name the subordinate concepts (kinds) in examples and practice. For example, suppose you were teaching the concept "woodwind instrument" in music, and your only objective was for the learners to be able to classify any musical instrument as a woodwind or not a woodwind. Many novice designers would say in an example, "This is a clarinet, so it is a woodwind." Or they would say in their feedback, "No, this is an oboe, so it is a woodwind." There is nothing wrong with this if the learner already knows what a clarinet or oboe is. But if a learner doesn't, then this just adds to the amount the learner needs to try to figure outóit makes learning more difficult rather than easier. Even when such subordinate concepts are also among your objectives, it is generally better to help them master the higher-level concept (woodwind instrument) first, and then teach its subordinate concepts. The subordinate concepts can be taught simultaneously with each other, as long as there aren't too many of them. Otherwise they can be taught in sets of 3 or 4 at a time. 

A second error novice designers commonly make is not indicating the criterion for mastery on the practice. This is important for both situations in which the learner will exercise full control over their progress and situations in which a teacher (or computer) will exercise such control.