The added pressure of him watching you. Without him there, you can cheat far more easily and your mind will wander. With him there, he keeps you focussed.

The only problem is when he is, for whatever reason, unable to watch you . In which case you may need another incentive to work. What if he were to send you regular text messages or e-mails to you (if he was away, for example) asking you for progress reports?

BTW, just as a general study hint, try drinking a lot of water and making sure you have eaten well. Even if you don't feel thirsty you can be up to 10% dehydrated and that significantly impacts your ability to concentrate. Also low blood glucose is another major thing that can affect concentration and cognitive ability so keep it topped up with long acting (slow release) carbs like oats. I know from personal experience (I am type I diabetic) that glucose levels can drop alarmingly just from a few hours of sitting quietly in an exam so it is mental as well as physical effort that uses up energy. It may be the result of either or both of these things that are causing you problems rather than any learning disorder though there is no harm in checking this out as well.