Massey University researchers set out to describe the type of bits used by riders in the general horse population in New Zealand.
Lauren Beanland, Chris Rogers, Erica Gee, Charlotte Bolwell and Stuart Gordon collected information in an online survey run for eight weeks from early December 2010, with 566 riders providing information on bit use for 971 horses.
Most respondents were females, from the northern districts, and had been riding for less than 20 years.
The most common competitive fields cited were dressage, endurance, eventing, show jumping and showing, with most at a novice/lower level. Most rode one or two horses aged seven to 12 years.
Overall, 75 per cent of respondents' horses were sport breeds, and 50 per cent were used for the common competitive disciplines cited above, while 31 per cent were used for recreation.
The most common bit used was a straight bar snaffle bit (85 per cent) of medium thickness used in conjunction with a cavesson (60 per cent) or flash noseband (32 per cent).
Sixty per cent said they used their bit of choice as they felt it worked best for their horse.
Fifty-nine per cent of riders who answered the survey thought there should be greater flexibility in the type of bit and bridle permitted in competition.
In all, information was gathered on the use of 1120 bits. Bitless bridles were used in 212 cases, with 41 per cent feeling it worked best and 28 per cent saying welfare was their primary driver.
The authors noted that evidence for the effectiveness or mechanism of many bit types was limited, despite bits having been in use for more than 4500 years.
"Much of the readily available information in the popular press is based on observation and expert opinion," they said.
The researchers found the most common shape of bit ring used with the three types of bit was "O-ring" (847 of 1002, or 84.5 per cent). "Loose" rings were most common with snaffle and gag bits. Most snaffle and gag bits did not have cheeks, whilst most leverage/curb bits were used with fixed cheeks.
Overall, most bits were straight bar (70.9 per cent), made from stainless steel (72.8 per cent) and of medium thickness (72.5 per cent).
Overall, 1113 nosebands were used with 1120 snaffle, gag or leverage/curb bits. The most common noseband used across all bit types was the plain or French cavesson (51 per cent), followed by the flash noseband (31.8 per cent).
Few drop nosebands (5.3 per cent) and crossed, grackle or Mexican nosebands (5.1 per cent) were used.
In total, 152 of 1120, or 13.5 per cent, of bits were used with running martingales and 30 of 1120 (2.6 per cent) were used with standing martingales.
The bit choice in 60.4 per cent of cases came down to respondents feeling their horses went best with it, while straight personal preference was the key factor in 20 per cent of cases.
In total, 63.6 per cent, 53.1 per cent and 20 per cent of respondents that used snaffle, leverage/curb or gag bits, respectively, reported that they would consider using a bitless bridle.
Of the 212 bitless bridles used, the most common was a halter (64 of 212, or 30.2 per cent), followed by a hackamore (57 of 212, or 26.9 per cent).
Cross-under bitless bridles were used in 42 of 212 cases, or 19.8 per cent; 29 of 212, or 13.6 per cent used sidepulls; 10 of 212, or 4.7 per cent used mechanical hackamores; eight (3.8 per cent) used bosals; and two (0.9 per cent) were classed as other types of bitless bridle.
A loose ring snaffle.
"The snaffle bit is widely used for the basic schooling of horses within equestrian sport and is a requirement for lower-level dressage, which may explain the apparent dominant use of this bit in the study population."
They continued: "Interestingly, the main reason for the use of the current bit for the horse and rider combination was 'the horse worked best in this bit', implying that after initial training there is little change in the bit used on the horse."
They noted recent research that indicated a major contributor to behaviour with a bit related to rein tension rather than bit action.
"This implies that the rider's ability to provide a constant and acceptable rein tension is one of, if not the most important, contributors to bit acceptance and may explain limited variation observed in bits used."
The researchers said a possible confounding factor for the low level of use of the bitless bridle is limitations on its use in equestrian sport.
"At present, only the jumping disciplines permit the use of a bitless bridle, with dressage requiring the use of a snaffle bit.
"Internationally, some national equestrian federations have relaxed regulations regarding the type of bit used and this may be associated with the finding in this survey that 54 per cent of respondents felt there should be greater flexibility in the type of bit/bridle that was permitted for use." The study was entitled "The use of bits in the general horse population in New Zealand".