The world is full of stimuli that can attract our attention through various senses. The environmental stimulus is everything in our environment that has the potential to be perceived.
This might include anything that can be seen, touched, tasted, smelled or heard. It might also involve the sense of proprioception, such as the movements of the arms and legs or the change in position of the body in relation to objects in the environment.
For example, imagine that you are out on a morning jog at your local park. As you perform your workout, there are a wide variety of environmental stimuli that might capture your attention. The tree branches are swaying in the slight breeze; a man is out on the grass playing fetch with his Golden Retriever; a car drives past with the windows rolled down and the music blaring; a duck splashes in a nearby pond. All of these things represent the environmental stimuli, serving as a starting point for the perceptual process.