The more interactions the infant has with people and objects, the quicker the concept of cause and effect will be learned.
Granted, after one year, many smart babies begin to use crying with wily intent and parents have to use their discretion to maintain their autonomy.
The more interactions the child has with the parents and other extended family, the more the role of cause and effect in our lives can be demonstrated to the child.
It would seem here also that the more objects the child is allowed to come in contact with (toys in particular) the more opportunity there will be for the infant (child) to explore the phenomenon of cause and effect. The toys don’t have to be elaborate or expensive to be effective!
They may be just household objects, like just a piece of cloth or a blanket, which the child will turn into a myriad of make-believe toys. Of course, parents must monitor the flow of these objects so the child is not inundated with them all at once.