The reptile brain: this consists of the olfactostriatum, corpus striatum, globus pallidus and satellite connections.
The reptile brain controls basic survival instincts: fight-or-flight, hunger, territoriality, ritual and challenge displays. The reptile brain, by itself, may or may not permit herd behavior, but interaction in the herd would be reduced to functioning within a pecking order. Newcomers to a territory, held by members of their own species, have only two options: fight or move on.
The mammal brain: made up primarily of the limbic system (also found in birds).
The mammal brain makes possible pleasure, the maternal instinct, love, and compassion, all of our higher emotions. The limbic system makes it possible for herd interaction to go beyond the pecking order. Herd members care about each other, groom each other, look out for each other, and may even put their own lives on the line for the protection of the herd. The mammal brain allows a level of conflict resolution. Newcomers to a territory, when they persist in their efforts, may eventually be accepted as members and even friends. It makes possible a tactile sensitivity that allows the individual, in grooming, to tune in to what the groomee is experiencing. Pleasure is not just subjective; it can be interactive and even empathic.
The human brain: the neocortex.
This, of course, is where our real problem solving and tool-making abilities reside. The neocortex allows us to organize information into concepts, represent them with symbols, and manipulate them in ways that not only give us practical advantages, but can also give meaning to our lives and actions. In cooperation with the limbic system, it also makes it possible to function, socially, completely outside of the pecking order.
First, let's look at a lizard's brain. It was one of the first steps to a central nervous system over something I will refer to as fused ganglia. Fused ganglia is a dense area of nerves that was a precursor to a central nervous system. Fused ganglia is commonly found in insects. Fused ganglia is found along the mid section back of an insect or where you would assume a spine would be if they had one. Besides heartbeat and other automated bodily functions (reflexes), fused ganglia offers instinct only! Eat, breed, social interaction (basic non adaptive), and response to external stimuli.
The lizard brain is not that much advanced. Without overcomplicating the issue with the Amygdala, Thalamus, and the Hypothalamus; I would have to state that the brain of a lizard is so simple, it is not self aware. It had the most basic functions with a few higher functions over fused ganglia.
These more advanced functions of a lizard's brain would also include social interaction. Don't misinterpret the term social interaction with what we know it as. It's more advanced brain would add territorial aggression and fighting. Remember that there is NO frontal lobe in a lizard. It has no idea why it fights. It has no idea that it is breeding. It's responses to outside stimulation (pain) is fully automated. BUT, it can adapt to outside stimulation. If you were to walk into a room with a bucket of cricket’s everyday at 3PM, the lizard does not know that you are walking in with a bucket of crickets, but has associated the action with food. Some misinterpret this as cognitive thought. This is very basic association to external stimuli.
Now to get to the statement of "being cruel". Lizards do not know the concept of being cruel. Lizards do not cuddle. Cuddling is something that advanced mammals are capable of. Lizards are not self aware and certainly are not aware that there is a female next to them. If anything, they would only display the automated breeding or fighting response offered by its limited brain functions. Your lizard does not love you or care for you. If you sold it tomorrow, other then an adjustment period to its new surroundings, you would be forgotten the second you handed it over. Lizards do not have emotions. Lizards do not think.
Keeping a lizard by itself eliminates the possibility of injury because of its territorial aggression response. It has no need for companionship. It does not feel lonely or bored. If it bites you, it does not hate you. Emotions are beyond its capability. If it were aware for a second of any cognitive thought, it would appreciate the fact that you gave full use of your own frontal lobe and provided safety for it and not imposed your own higher brain functions on it.
