Intelligence is an entitie's ability to process sensory data, and derive useful information from it. Any living thing has some level of intelligence, some cognitive scientists would even argue that a simple device, such as a thermostat has some minimal level of intelligence.

Intelligence requires the ability to sense information, process the information, and normally derive some useful action or conclusion based on the information processed. It is not correct to say some animals are intelligent while others are not. All organisms have some level of intelligence; the degree of intelligence is a measure of magnitude, not a boolean function. A plant has intelligence when it turns its leaves towards the sun. An ant has intelligence when it follows a chemical trail to forage. A dog has intelligence when it hears its name called and comes. A human has intelligence when he or she uses tools to change its environment to their needs.

Why is intelligence important?Edit

When deciding what is legal or ethical to kill, or what rights an entity has, one must have some criteria to evaluate. One could choose to subscribe legal rights based on size, age, color, gender, species, longevity, intelligence, ability to suffer, or many other criteria. To base an entities legal rights on color, gender or species does not seem logical, even though each of these have historically been used to grant different legal rights among humans, and in some countries still are.

To grant legal rights based on aesthetic qualities of an entity such as its size, or color is illogical. Historically humans have been granted rights based on these, but this for the most part has ended in the modern world with the ending of Apartheid in South Africa. Should an Elephant have different rights than an ant, based solely on size? Logically not, but perhaps for other reasons.

Granting rights based on gender, if the gender does not account for a significant difference in intelligence (it is possible that it does in some species) does not make sense. Historically humans have been granted rights based on gender, and in many countries are still given different rights based on gender, but this practice seems to be ending.

Granting rights based on age may make some sense, as intelligence changes with age, many rights such as voting and drinking are granted based on age.

Granting rights based on longevity may make some sense. To kill something that has lived for centuries and may live many more does seem less ethical than killing something that only lives one day. Although longevity may have some influence on logical rights, in would be minor at most, and would not be logical to be the main criteria. Should a tree be given more rights than a human because it lives longer, logically not.

Granting rights based on species does make sense, because different species have different levels of intelligence. However, if two species had equivalent intellect, it would be illogical to give them different rights. This however is commonly done, in that in most modern countries dogs have different rights than pigs, but the intelligence of the two species is comparable.

If a chimpanzee were biologically modified to increase its intelligence to be equal or greater to that of a human, should it be granted human legal rights? Logically it should. So it is intelligence that is important, not species. A tree is more intelligent than a rock, so should it have different rights? An ant has more intelligence than a tree, so should they have different rights? A mouse has more intelligence than an ant, so should they have different rights? A pig has more intelligence than a mouse so should they have different rights? A human has more intelligence than a pig, so should they have different rights? The question is, what rights should be given to each level of intelligence?

Some argue it is not an organism's intelligence that is important, but its ability to suffer. However, how does one define ability to suffer, other than through its intelligence, memory, self consciousness, and prediction which all play an important role in suffering? It's not just about suffering either. You can kill an animal or a human painlessly, but it is still wrong, an intelligent animal deserves the basic legal right to life.

How to measure intelligenceEdit

In humans, one typically attempts to measure intelligence using an IQ test. But, even in humans this is generally a difficult task and prone to inaccuracy. What exactly any particular IQ test measures is also an area of debate. Some measure cognitive reasoning, others linguistic ability, or mathematical logic, pattern recognition, memory, or creative thinking. The main issue is there are many different types of intelligence, so some people, or animals may do better in some areas, but worse in others. Humans are the most intelligent animals in many areas, but if your IQ test was based on auditory processing, we would probably lose to dogs and most other mammals. For visual processing we would lose to cats and bird of prey. Even for linguistics we would loose to dolphins (which have been known to understand some words in our language, but we have yet to understand theirs.)

So how do you classify the intelligence of other living things? Intelligence in animals emerges from the interplay between neurons in the brain. If you remove the brain, or part of it, then you remove intelligence (or part of it). So this is a good place to start, living things without brains, probably have less intelligence than living things with brains. Most animals have brains, or at least some neurons. Plants and fungus do not. The evolutionary paths of plants and animals diverged before neurons existed (actually before multi-cellular organisms existed). Now it is entirely possible that plants evolved some different form of intelligence other than a brain and neurons. Plants do have the ability to sense and respond to changes in their environment, as do all living things. Plants do not have anything similar to a brain or neurons, but I would not rule out their ever evolving intelligence in the future for intelligence is a useful adaptation.

So, if we start with plants and other non-animals at the bottom, because they have no brain or neurons, we can then move on to classifying animals. A good start is animals with a brain versus animals without a brain. Most animals, even insects have a brain, some worms and invertebrates like some clam specifies do not have a brain, but do have some neurons. So we can put invertebrates without a brain at the bottom. For animals with a brain we can start to organize them by the number of neurons. Some slugs have only 250 neurons, and some bees have almost 1 million, and octopus have 300 million and is probably the most intelligent invertebrate. Vertebrates have much larger brains, and are generally more intelligent. The bigger the animal, generally the bigger the brain, but this does not necessarily mean more intelligence, as a bigger body seems to require a bigger brain to manage it. Humans have around 100 billion neurons and a brain that weighs about 1300-1400 grams. Whales and elephants can have brains 4000 to 8000 grams, but are not generally more intelligent. The ratio of brain size to body size is more accurate determination of intelligence. If you make some adjustment for size you can arrive at several formulas for approximating the general intelligence of a species. It's not just size that matters, but also complexity, organization of the brain, and speed of the neurons. Even with a very small amount of neurons it is possible to achieve some intelligence, but in general the more neurons available the easier it is, especially in terms of storing memory.

Chart ordering species by relative brain sizeEdit

Species Encephalization quotient (EQ)
Rhesus monkey2.09