After reading through the material, I would define interaction as a “conversation” between user and product in a way that stimulates input, processing, and output from the device to user and vise-versa. This can occur in varying degrees, but these fundamentals must be present in order for there to be interactivity. What makes the interaction memorable is when the device truly “listens” to the user’s inputs, contemplates and processes that input (probably within milliseconds) and then creates an output based on that input. A good example of this for me personally was Super Mario Brothers on my old Nintendo Entertainment System. It is not necessarily the greatest example, but it takes your inputs of the controller, processes through them, and gives you a visible output on screen to make Mario move. Not only are you giving inputs that generate outputs, but so is the game, such as through the enemies that appear on screen. It sends you the input that there is “danger” which requires you to process an then react, generating an output. You have to make the decision whether to jump on the Goomba, avoid it all together, or just let it run into you causing the poor plumber’s death. The game’s Input generated an Output from the user. You and the product are both influencing each other, creating interactivity. In regards to the statement that “interactivity is not easy to achieve”, I would agree to only an extent. Personally, I think interaction is not too terribly hard to achieve. Look at the refrigerator light example, that is definitely a form of interactivity, even if to a very low degree. However, it is not very memorable or “good” interactivity. That is where I would say the true challenge of the issue comes from. Not creating interactivity, but generating truly influential and memorable, genuine interactivity.