Years ago, human beings were not persuaded or affected by images the way that the world is today. It would be a difficult task to go even a small amount of time without seeing an image or a symbol that has influenced the way that we think as people. Even for people who don't own televisions or computers are impacted by the image of something frequently. With the progression of technology and our reliance on the media to provide us with information we have unknowingly allowed images to control the way we think.
For most people, a day or even an hour or two without seeing an image would seem almost like a form of sensory deprivation. Images are wired into our brains so that we see certain images even while we sleep. When someone sees a universal symbol of something, they don't even need to think about what it means. That is because we are so familiar with tons of images and see them so frequently that we don't even have to contemplate what they mean. If someone changed the bathroom symbol for the ladies room to a symbol with pants instead of a dress, we would be forced to think about which restroom is designated for which sex.
In a way, I think that the overabundance of images in our world is making us lazy thinkers and we are being manipulated unconciously to think certain things that we otherwise wouldn't at the control of others.At the same time though, an image is a very powerful tool and when used correctly, they inspire us to further our thoughts. That is the purpose of art many graphic designer's work...to inspire us to think further into images and what they mean and develop our own ideas about what a picture is saying.