Cognitive Science: An Introduction/Senses In Non-human Animals and Robots

Single-Celled Organism Perception

Very early on in the evolution of life, single-celled organisms had a primitive kind of perception, as single-celled organisms still do today. The surface of the cells had detectors that could identify chemicals in the environment. If the chemical was something good, like food, then the organism might move in the direction that had a higher concentration of that chemical. If the presence of a chemical is higher in some areas, and lower in others, this is known as a chemical gradient. Similarly, harmful environmental conditions, like extreme heat, cause small organisms to move away. This is the biological origin of perception. But single-celled organisms are too small to detect which direction the gradient is facing. What they do is they have a very primitive memory with one slot in it. The bacterium will swim straight ahead as long as the desired chemical magnitude is greater than that in memory. Otherwise it changes course.

Single-celled eukaryotes often have more complex perception mechanisms, including a primitive kind of light detection. They have eyespots that are sensitive to light. They will move toward or away from light depending on their energy needs in the moment.

Multicellular organisms (humans included) have much more complex sensory systems.

Detection of Polarization of Light

Octopuses have, as a part of their visual system, the ability to detect the polarization of light. Light is made of waves, and the plane of the oscillation determines its polarization. Certain sunglasses work by only allowing certain polarizations to get through, so when you turn your head, you can sometimes see some light blocked but not other.

Echolocation

Many bats use echolocation to navigate in their environment. With practice, human beings can do a limited version of this as well.

Electrolocation

Platypuses and electric eels can detect electrical fields given off by other animals. They use this sense to detect prey.

Magnetoreception

Magnetoreception is the ability to detect Earth's magnetic field, so that the individual can tell which way is north. Many bacteria have this sense, as do many fish, amphibians, reptiles, birds, and, rarely, mammals such as mice, mole-rats, and bats.