(18)As some of the investment products within the scope of this Regulation are not simple and may be difficult for retail investors to understand, the key information document should, where applicable, include a comprehension alert to the retail investor. A product should be regarded as not being simple and as being difficult to understand in particular if it invests in underlying assets in which retail investors do not commonly invest, if it uses a number of different mechanisms to calculate the final return of the investment, creating a greater risk of misunderstanding on the part of the retail investor or if the investment's pay-off takes advantage of retail investor's behavioural biases, such as a teaser rate followed by a much higher floating conditional rate, or an iterative formula.