People, dogs, cats, and other animals all respond to their environment. Based on what they perceive with their five senses, their emotions and their body change—their hormones, brain waves, heart rate, even their pH. Information from their surroundings more obviously changes information in their mind, adjusting their perception of themselves and the world.
Humans and other animals have an important difference, however. Unlike other animals, the brains of human beings have a kind of sixth sense, an awareness of who they are. Because of this meta-awareness, people are capable of changing their thoughts and emotions based on their intention.
I spoke a lot on this subject as I toured the United States this year and spoke at screenings for my film, CHANGE: The LifeParticle Effect. Take a look at this clip from the lecture I gave at the Tsai Performance Center of Boston University on June 11, 2013 to hear a bit more on this topic.