HCD.19:3 - Forces

• A natural open-book task can be representative even when a worked example is nearby; answer proximity still limits what the result establishes.
• First recognition and successful correction are both useful, but a later cue can erase the opportunity to observe the first.
• Expert inspection can reveal a subject defect cheaply, while audience-dependent adequacy requires evidence from the relevant reading conditions.
• Whole-route claims need connected reading; a local repair should reuse unaffected evidence.
• A teacher can legitimately supply a promised contribution. Requiring all help to reside in the material changes the product being evaluated.
• Useful difficulty may prepare later instruction, whereas unsupported difficulty can leave the task impossible. The next instructional move distinguishes them.