HCI is a field which contributes technology without any discrimination and and satisfy users in any of the context. For Senior Citizens, the special preference must be given to the accessibility level because a more accessible product is usable for all and poor usability distract any of the user. Also the focus must be given to the cognitive burden because cognition is the process in which user learns and things move from short term to long term memory so to reducing the burden can also enhance the learning process.

Hi Nazir - I agree with your comments - especially in regards to accessibility. The probable solution ( I suspect) requires a strong focus on usability by Seniors, and therefore by default it requires a strong focus on accessibility. Mobile devices pose a number of solutions - but at the same time can also appear as constraints in the form of font size, tablet size, and smart phone size. The technology using mobile applications has already grown many of the global HCI tables exponentially, but the physiological and mental barriers that trouble seniors as late adopters are much harder to overcome. I agree that cognition needs attention. early studies have shown the difficulties in getting Seniors to engage with ( and trust) new developments such as online financial banking.

Here i want to sugesst that u must select some tasks and and gives a presentations to some senior citizens to perform that tasks. Then on the basis of that tasks , select some questions and asks that group of user to fill that survey about that respective tasks they perormed. Also ask them to give feedback in the language they express easily. The main gap is there is no communication between designer and user which creats complexity. As user has no concern abt complex functionality. They want a usable and accessible interface. The main thing is to collect the data abt user needs . Then to work again on the devices or anything else u want. Because in HCI our focus is user. And user only visits ur site or use ur device if it is accessible and handling as user friendly. There must be special prefernce to user's mental model because all users from different cultural backgrounds and different mental capabilities, handle ur devices ur sites according to their own pace. Hopefully helpful for u.