There is often a mistaken assumption that thought (and therefore emotion) are intrinsically linked with language.

So the assumption says that babies (who can't speak) are not thinking and therefore not experiencing emotion and therefore not attracting the results of what they are thinking. (This mistaken assumption applies to animals too).

Babies start attracting to themselves in this physical reality from the moment their consciousness projects into the physical body, which is normally with the first breath.

Left to themselves, they would live happy and joyous lives...but there is a conditioning process that happens (from older humans) that often influences them away from that.

See How does the law of attraction work in regards to children? for more information on this.

However, we are these days (in response to that) seeing more children being born who are more resistant to this form of societal conditioning.

So we are seeing greater and greater conflicts happening between the youth and the establishment as the young people try to maintain their freedom of thought (and expression) and the older ones push harder and harder to get them to conform.

From the moment of conception, we start dowloading information including perceptions, from our parents and other caregivers. If we 'inherit' a perception that we will be abandoned or neglected or mistreated, then we attract people who will fulfill those expectations. It goes all the way down to the vibrational level though, so it's not like they are thinking words or even picture to express these perceptions, they are just vibrations that attract like vibrations.

My children were encouraged to have "wish books" when they were young, similar to what I had myself. So in our household, we were excited to get new catalogues, magazines or Sunday newspaper ads. They could clip out photos of things they wanted and would put them into their photo albums to look at before bed. I would have them imagine some scenario in which they had the actual item and tell me all about it. This made for a lot of positive family fun and helped them gain confidence in their manifesting skills and learn concentration and visualization. Both kids, although only in their twenties are doing quite well in all aspects of their lives, which I am so grateful for.

Young children can and do manifest, and with some encouragement from adults to really develop the skill, they will really shine.

Additionally: I realize I didn't answer your questions completely and should add this. Children are much like sponges, so if they are constantly seeing negative examples around them, or hearing negative words and ideas from those whom they trust, they will also manifest more negativity into their lives. But bad things happening in their lives are not always the result of manifesting. Sometimes it is karma, or circumstances beyond their control, something they chose pre-life to round out their character, the result of someone else's free will or whatever. It seems there are many ways for good and bad to show up in our lives. I am not sure at what age they can conciously manifest, but I will be interested to see what others say about that too.