How about coloured icons to make card ratings more intuitive?

I know you've spent a huge amount of time creating a very user-friendly interface so I thought you might consider this to make it more intuitive.

How about adding coloured backgrounds to the ratings icons, or even colouring the icons? I would suggest a gradation from green ("perfect") through to red ("unknown"). I think this would make it more intuitive to rate each card.

The more green your rating, the happier you would be to keep going through to the next card. The redder your rating, the more likely it would be flagged as something you still hadn't picked up and perhaps needed to pause (or "stop") on for a while longer.

If a learner is struggling with a certain card, I think they should be encouraged to properly encode the association between the question and the answer. Having them flag a card with a red rating might be one way to do this.

The reason for red and green is that they're hard-wired into the human brain so don't require extra "cognitive load".

The colour scales used in GetSatisfaction might give you some ideas.

Cheers,

Dougal