The first hypothesis is that synesthesia is the result of less "neural pruning" in the brain while in utero. Neural pruning is the process of removing synapses that are no longer used or helpful to the brain. It's a natural process in the brain that happens at different developmental stages of a young human. Children's brains grow quickly and in the surge of growth and learning, neural pathways are created that are useful in certain stages, but not all. When the pathways are no longer useful, they die off so that the stronger, more useful synapses may be used instead for a more efficient functioning of the developing brain (Monteiro, 2010). If less neural pruning occurs in a synesthetes brain, then there is naturally an increased number of neural pathways that may trigger more than one sense at the same time, leading someone to taste the sound of trumpets, for example. Daphne Maurer, PhD, a psychologist at McMaster University, has hypothesized that all people are born with the neural connections that allow for synesthesia, but that the vast majority of us lose those connections as we develop and grow (Carpenter, 2001). Another hypothesis as to how synesthesia came to exist is that it is simply genetic. Psychologist Peter Grossenbacher, PhD said, "We don't need to posit some abnormal architecture of connections in order to account for synesthesia." Instead, he suggests that in the brains of synesthetes, connections that carry information from multiple sensory areas of the brain back to single-sense areas are not properly repressed (Carpenter, 2001). In synesthetes' brains, that repression is prevented somehow, allowing the different senses to become scrambled. "The possibility that synesthesia has genetic roots is equally tantalizing," says Grossenbacher, "especially if it turns out that a single gene controls the condition, as some have speculated. If indeed synesthesia is controlled by a single gene, this might be rather a new kind of gene to know about.