How I jump to my conclusions

Usability testing with children is similar in many respects to usability testing with adults.
But in order to get the most out of the sessions, and ensure the child is comfortable and happy, there are a few differences that you need to be aware of.

(Read about in on Tim Fidgeon's Feature: Usability testing with Children)

Among the differences that drew my attention were the importance of non-verbal cues, because

• Children might be too shy
• Children might not want to say the wrong thing and displease an adult
• Children might say things they don't believe just to please the adult

So its very important to be sensitive to children's non-verbal cues, such as:

• Sighs
• Smiles
• Frowns
• Yawns
• Fidgeting
• Laughing
• Swaying
• Body angle and posture

I personally think the whole article applies equally well to Usability testing with Older people.