What is join-up and how did Monty Roberts develop it?

Join-up is Monty Roberts's method for establishing initial communication and trust with an untouched or fearful horse by using the horse's own social body language to invite the horse to voluntarily choose the trainer's company rather than flee — a process that transforms the trainer from perceived predator to accepted companion through a specific sequence of communication exchanges in a round pen. Roberts developed join-up through decades of observation and experimentation, beginning with his teenage observations of wild mustang herds in the Nevada desert where he studied the specific body language exchanges that governed herd social dynamics. He observed that lead mares used specific threat postures to drive misbehaving herd members away — a squared-up body, direct eye contact, active driving energy — and that the driven horse communicated its desire to rejoin through specific submission signals: licking and chewing, lowering the head, turning an ear toward the mare. When the mare accepted these signals and invited the horse back, it would join up with the group. Roberts adapted these observations into a method for working with untouched horses in a round pen, using the same body language exchanges to first drive the horse away and then invite it to join up with the trainer rather than with the herd. The specific signals Roberts watches for — the inside ear locking on the trainer, the head lowering, the licking and chewing — indicate that the horse has shifted from a flight-aroused defensive state to a socially engaged state ready to accept a new relationship. The process has been demonstrated publicly thousands of times across Roberts's career and forms the foundation of his approach to starting horses, gentling fearful horses, and addressing behavioral problems.