My daughter Sydney is about about two and a half at the time of this post. In that time she's only known the iPhone as as a toy and Mom and Dad's cell phone of choice. So for her mimicking her parents meant sliding her finger across the screen and (hopefully given that Mom and Dad had not set the password parameter up) wah-lah a wonderful little world of colors and squares that did things when touched. She had figured out how to access the main menu before she turned one.  Watching this dance was not only fascinating but frightening as the user interface (UI) is so incredibly intuitive she was literally fishing through applications with no little no understanding or caring of what they did. To her it's lights, sounds and wonder; to me however, it was usability testing 101.

I guess I should have seen it coming seeing as the rubber shell for my iPhone (gen one) was her first chew toy. That being said it's been fascinating for me to watch my Princess bang around apps with not a care in the world of what it does. I repeat that point because as a designer/developer we're often so tied to the outcome we forget the passage. For her it's all about 'what can I make it do.' Her primary interest initially [seemed] simply to click to the next screen. Therefore, from a foundational UI standpoint she's the perfect tester.

Here's a list of simple truths I've observed:

• When you make the same button in the same location do two different actions it immediately becomes confusing (e.g. YouTube's login and Sign Out on the same button)
• Differentiate with greater detail what you want people to do with colors, shapes and sizes
• Give 'call to actions' (CTA's) screen prominence and visual triggers
• Show a brief demo of where to click and the ensuing action it creates
• With children's applications use audio as a key driver for delivering action and reward
• With children's applications don't forget that things [should] be silly and whimsical; I've come to note a couple of elearning apps that have failed to be "fun" and have garnered only seconds of my daughters attention
• Keep it simple and light. You're not using this thing to hack into the Kremil and stop a bomb from detonating
• Never presume! Never think that the user knows your brand, product or in any way how your applicaiton/website should work, feel or react
• Children's applications often have a lot of repetitious content and while this is good from a cognitive standpoint remember that their attention span is very short if not captured
• Lastly, how many times has it actually been repeated played? I'm of the mindset now that if I get a-play-a-day for a week it was worth the $.99 download – especially if she genuinely learned something along the way

Another item to note is that if you truly intend to "teach" with an application that it's incredibly important to hire an instructional designer. While they cannot design the outcome of the education it is crucial at the very least the material to be learned can be conveyed with proper instruction. It's important to note the type of child/person that you're building the material for as well. Instructional designers will take different paths to maximize the success of different kinds of learners such as autistic, ADHD and other special needs scenarios.

Lastly, since now that Mom and Dad have migrated to a G3 she's one of the few two-year olds blinging' an iPhone full of great applications like:

• Dr. Suess
• Animal Sounds
• Old McDonald
• Talking Carl

More from a recent article in Fast Company:

Since its initial release in 2001, the iPod has received acclaim for its easy-to-use interface. Now, with the release of the iPad, we wondered if Apple's latest product was so simple even a 5-year-old could use it. Here is our completely unscientific hands-on research.