questions of the subjects and their parents. The questions asked included information about the child, such as age, whether the child has had a near death experience, and where and how often the child sees the ghost. The questions also include ones relating to the child's experience with the ghosts, such as the content of the interaction - if the ghost asked favors of the child, if anybody else in the family had seen the ghosts, and if the child felt threatened or was told not to tell their parents about the visits. The final set of questions asked about the appearance of the ghosts. Each set of questions asked subjects to elaborate on each answer, in order to fully understand the child's ability and experiences.
The study concluded that the for the most part, a child's ability to see, hear, and speak to ghosts peaks anywhere between 6 months and 4 years of age. This seems to be because this is the age before children are told that what they are seeing is a ghost, and to them it is as normal as interacting with the living. After the children become aware of this, or told that ghosts are just "in their imagination," they tend to ignore their ghosts and lose their abilities. This tends to happen between the ages of 5 and 11 years old.
The study also concluded that, according to descriptions by children and family, children are more than likely visited by family member that passed away long before they were even born. The children tend to see these ghosts in full body apparition form, and are therefore able to fully describe the figure to family. It is believed that these family members are simply watching over the children until they feel that the child no longer needs their protection (take a look at "Why They Hang Around" to find out more about this, and other reasons ghosts stay in the living world). This would also explain why most children lose their abilities between the ages of 5 and 11, for this is the age that children begin going to school and learning more about right and wrong. They are better able to take care and look after themselves.
The study includes several examples of answered surveys from several subjects, as well as photos submitted by subjects. One mother filling out the questionnaire notes that her 3 year old sees her grandfather that had been deceased for 13 years. The 3 year old tells her parent that "he keeps her safe."
It is a simple conclusion. Babies and children are not the only people who see ghosts. They are simply the only people who admit it. They have not been told that ghosts aren't real, and are therefore open to seeing and speaking to apparitions.