Is it true that frequent wakings in the night means baby tends to be more intelligent?

It is a myth but a good one at it. The reason behind frequent night waking is as mentioned by polar mummy77, related to the baby’s sleep cycle and need for feeding. Still, for parents who take to this argument, it probably makes the frequent wakings more “bearable”. Also, if one believes that his/her child is more intelligent, there is a chance that the parent will create a more stimulating environment for his/her child. Only (potential) drawback I could think of is the additional pressure for the child to perform in the near future.

That's clearly a myth. Most babies experience frequent night wakings. Babies have shorter sleep cycles, and they spend proportionally more time in “active sleep," the baby equivalent of REM. They also have smaller stomachs, which means they need to eat more frequently than adults do. Put these traits together, and you get a creature that sleeps lightly and needs to awaken every few hours.

thanks