Headmaster technology is a technology introduced introduced in season 4 of the The Transformers television series. It is the first such example Binary Bonding, whereby a smaller being (a Headmaster partner) would form the head of a Transformer (a Headmaster).
While some Headmasters have commented that they have felt a closer bond with their respective Headmaster partners, there is no reason to believe there is any true psychic connection between them.
The idea of an organic humanoid assisting a Transformer was thought up by Brainstorm when he observed a race on Cybertron where Hot Rod beat Blurr. Brainstorm's hypothesis was that Hot Rod won the race because Daniel assisted him. Daniel had worked the pedals whereas Hot Rod steered.
When Optimus Prime communed with Alpha Trion through Vector Sigma. Alpha Trion mentioned the union of an Autobot with that of a human being. Optimus Prime believed Alpha Trion was speaking nonsense.
But it would not be the homeworld of the humans where Headmaster technology would first be implemented, instead it would be the far world of Nebulos populated by the Green-skinned Nebulans. After some of the Autobots who had crashed on Nebulous were taken prisoner by the Decepticons. The remaining Autobots teamed-up with a resistance faction of Nebulans and agreed to undergo the modifications made by Spike and Brainstorm. Some Autobots were concerned about losing their personalities but Brainstorm explained how that would be solved. Daniel, who had been injured partnered with Arcee. Cerebros refused to take part due to his pacifist beliefs.
The Decepticons would later win back the key to the plasma energy chamber as Zarak joined the battle in a colossal Scorpion robot that transformed into space shi. He and the Decepticons then journeyed to Cybertron where they would proceed to join a battle where the Autobots were already suffering a lot of casualties.
Despite disagreeing with the original plan, Cerebros eventually became part of unique implementation of Headmaster technology; a double Headmaster. Spike had rebuilt a Hive city into a space ship. They would return to Cybertron when all hope for an Autobot victory seemed to be lost and the space ship transformed into a giant body. Spike became the head of Cerebros and Cerebros then combined with the body to form Fortress Maximus. Unlike the other Headmasters, Fortress Maximus did not appear to be sentient and only has two minds; that of Spike and that of Cerebros. For most of the fight it was apparent that Spike had the most control over the body, this was appropriate given Cerebros's pacifist beliefs.