First let us dispense with the Parelli merchandising on the subject, which I think has done a very interesting idea a lot of harm.
From Parelli you can buy horsenality tee shirts, mugs, toys etc etc. I might add that these days the vast majority of Parelli profits go into scholarships for students. Up to 100% of their fees are paid on a means tested basis. So this merchandising does have its' upside
James Roberts felt that the best thing to do with the tee shirts was to use them as dishcloths and never wear them. That does NOT mean he did not subscribe to the horsenality model, just that as an instructor he heard too many people use it as an excuse for not being able to perform certain tasks with their horses. It also tended to make people think of their horses as locked inside a horsenality box which will never change. That is not, and never was, the intention of the model, it is just how some people chose to interpret it in order to give them those excuses. His real pet hate was the fact, and I have heard it myself, that at a Parelli meet when starting a conversation with a stranger the conversation often starts "Hi, my names X and I have a left brain introvert".
Horses live in the moment, and so do their horsenalities. They will have a predominant horsenality, which under stress they will tend to revert to, but they can display any horsenality on the chart at any given time. This is similar to humans. I am inherently a left brain introvert which means I think a lot, don't act from fear much but in general can be pretty quiet. Get me into a place like this forum and I become a left brain extrovert, probably saying rather too much but in thoughtful sort of way.
The aim of the horsenality model is to analyse what horsenality is being displayed at any one moment and then modify your approach to that horse to bring it into a calm, forward thinking (not just forward going), left brain state of mind. This is near the center of the horsenality chart, but erring to the left side.
Let's take a look at the chart. http://www.horsechannel.com/images/h...alitychart.pdf . The idea with this chart is to put a dot in each behaviour pie at the place you think it belongs. Then, once the chart is complete have a look at where the greatest concentration of dots lie and that gives you an idea of the horsenality of that horse. There will be dots all over the chart, but chances are there will be a cluster as well. Filly was originally an Right brain extrovert, as she gained confidence with me she became Left brain extrovert, and has now settled nicely in the cusp of Left brain introvert/extrovert. That is in a familiar environment. Take her somewhere she is not used to and she can become extreme right brain extrovert again.
A word of advice on filling in the chart. People tend to know what horsenality they want their horse to be and fill in the chart with confirmational bias. To avoid that get a partner to randomly call out the attributes and answer, none, mild, moderate, extreme. The partner then fills in the dot. Make sure you cannot see the chart until it is complete. Don't do it just once, horses change over time so do it on say a three monthly basis to chart the progress you are making in getting them left brain near the center.
Make sure you learn all the horsenalities and approaches they need as the horse will change from minute to minute, but probably be the predominant horsenality most of the time. It would be a shame if you had managed to move you right brain horse to a left brain state for a while, but then did not know how to take advantage of it.
There is loads on the web about the horsenalities themselves so I'll only do a brief recap here, shamelessly cribbing from the web as I go
I'll suggest this site as a very quick overview and try and expand on it a bit Working with Your Horse
Right Brain Extrovert (RBE)
Extrovert means "likes to move their feet". Right brain means that they predominantly react instinctively and with fear. They don't use the thinking Left side of their brains. When horses spook and bolt that is instinctual RB (right brain) behaviour. The classic is for them to run from a lion attack. Standing around thinking about it gets them eaten, so they just react with no thought and run. They then go about 1/2 mile flat out then to save energy they stop, turn and face the threat and think about it in a left brain fashion to avoid wasting anymore precious energy that they need to. This turn and face can be thought of as a "pattern interrupt" which gives the horse a chance to think. We can use that knowledge to alter the way we play. I was teaching a 16 year old pony. When he started circling he would not stop, just kept going. He had been lunged a lot in the past and my circling him brought up bad memories and made him go RBE. I needed a pattern interrupt to get his LB to kick in for a split second so he could listen to my cues. I achieved this by travelling the circles so that he suddenly run into a fence, not literally. The shock of the fence appearing kicked his mind LB and gave me a second to influence him. After about five minutes of this he was listening to me much more and we could make progress.
Right Brain Introvert.
RB is already explained. Introvert means they prefer not to move their feet. To my mind this is one of the most dangerous horsenalities for us to deal with. An RBI will often not show outward signs of fear. They will look calm and composed and cope with their fear by trying to block it out and pretend it isn't happening. If you don't recognise this state and keep pushing on with the task then two things might happen. They could go catatonic, which is kind of a happy place prey animals go into when they know they are dead and give up fighting (apparently associated with large endorphin releases) or, much worse for us, they explode. Anyone ever seen a really calm horse that refused to move and was stubborn, then for "no reason" exploded into a bucking fit, threw the rider and headed for the hills. Of course there was a reason, they had gone RBI and been pushed just a little too far.
Left Brain Introvert
This is a real thinker of a horse. LB means they use the LB thinking side of their brain more than the RB side. Introvert means they choose not to move, but would rather stand still and conserve their energy. They have to be given a reason to do anything. They bore very very easy, then can become "naughty". The challenge for us when working with an LBI is not to get frustrated with them. We have to think up incentives to do anything. For example when teaching our LBI snappy upwards transitions the corner game worked miracles. This consists of asking him to only go from one corner to the next of the school. Once there he gets a rest, and maybe a treat. After just a short time, being LB, he figured out the game and put real effort into getting to the next corner for a rest (maximum around 7 seconds rest, or it is less effective). After a time we can miss out the odd corner rest and go two sides of the school and so on. Just to emphasise the "don't label your horse" aspect I would add he can be RBE in other tasks, so we approach them accordingly.
Left Brain Extrovert.
This is a fun horse, but can have a bit more go than many of us would like. He is always looking to play and have fun. He can drive field mates nuts with his hyperactivity. This horse needs lots of challenges. Quick changes of activities. He can be bored easily and then makes up his own games to play with you, so try (with the emphasis on try) to stay one step ahead. I like to have a good arsenal of pre-prepared ideas for this sort of horse as I can't make up new ones on the spot quickly enough. If you don't keep up they will tend to dominate you so be warned.
I'm going on holiday today, but will check back in next week to see how many flames this post has created. Of all the Parelli ideas this is probably one of the more controversial. I think that this is because they have over marketed it to some extent so that people have lost focus on its' true meaning and worth. Used correctly it can transform the way you deal with horses, especially if you get to play with a fair few which you don't always have time to really get to know intimately.