Vision Systems in Animal

Unlike the frog, humans have two visual systems. A more recent conscious visual system, that allows us think about what we see, and a much older subconscious visual system that detects things and makes us scared automatically. This older system is present in all vertebrates and connects with a brain area called the amygdala (CeA) to trigger fear when we see a threat.

Animals don't have to see all of a threat to be scared, this is one reason horses wear blinders. Just seeing a characteristic or feature of the threat, like a snake, can trigger fear.

What's weird is that the same feature that triggers fear can be viewed as food if it is oriented slightly differently. Thus there are subtle aspects of food and threats that cause us to behave a certain way.

Above: Mammals have a second visual system called the Superior Colliculus (turquoise) that sees key features of a threat (size, shape, movement, contrast) but does not necessarily form an image. The Superior Colliculus can activate fight or flight pathways quickly through a Relay (R, blue) in the midbrain to the fear integrating part of the brain called the Amygdala (purple). This occurs inconceivably quickly (information about visual threats reaches the amygdala in a few hundred milliseconds). From the amygdala the fight or flight system is activated via the endocrine (HPA axis) and nervous system (SNS) routes.