The Science of Hair Whorls and Laterality Part 3, The Nature Side of Nature/Nurture Early Experience, Debunking the Imprinting Myth

I devote part three of the series to a research study by Séverine Henry, an academic researcher from the University of Rennes, France, entitled Long-Term Effects of Early Intensive Handling of Foals (2009). I wrote this summary for our book, “Genetics and the Behavior of Domestic Animals,” 2nd Edition (2014), Chapter 7, “Genetics and Horse Behavior (Equus caballus) Mark J. Deesing and Temple Grandin. This research is important to anyone with an “imprint trained” horse or thinking of doing this procedure on their newborn foal. This groundbreaking study monitored the behavior of “imprint-trained” foals in normal social groups with adults and peers from early development to adolescence. Temple Grandin, myself, and other equine behaviorists never thought this procedure was a good idea—in theory or practice. The results of Dr. Henry’s study are both startling and disturbing. The work explains much of the mental illness in horses I noted in my journals over ten years. As a qualifier, “Imprint Training is a misnomer. True imprinting is a case of mistaken identity, only possible with animals like chickens, ducks, and geese, but not in horses with a more complex brain. A better possible definition of imprint training is desensitizing. For this text, I use (IT) for the reader to easily identify the foals handled at birth and those without this early handling procedure.

Long-Term Effects of Early Intensive Handling of Foals

The subjects were 19 French Saddlebred mares and their foals (11 females, 8 males), all maintained under the same conditions until birth. Delivery of the foals was not assisted, and all foals received minimal care apart from applying an antiseptic on their umbilical stumps. After birth, the foals were divided into one of two treatment groups: the control group, which included foals and mares left undisturbed (except for antiseptic application), and the experimental group, which included foals that had been handled following the “imprint training” (IT) guidelines of Robert Miller, DVM, (1991) “Imprint Training of the New Born Foal.” Apart from the early experimental handling procedure conducted on the handled foals (IT), both handled and non-handled (control) groups received only limited human contact necessary for routine procedures (mainly feeding and changes of pasture). They were kept under identical management, and the groups were mixed on the same pasture. The handled foals (IT) were later observed at four stages of life: during the early postnatal period, at six months of age with their mothers, at weaning, and at one year of age.

Early Postnatal Period

Handled foals (IT) stood up and suckled significantly later than control foals and also displayed abnormal suckling activity. This suggested a delay caused by the handling procedure rather than a lowered capacity. However, handled foals (IT) displayed short-term disturbances not seen in the non-handled foals, such as fast breathing and excessive trembling, indicating that the procedure significantly delayed these first two developmental stages. The abnormal suckling behaviors included excessive chewing and teat seeking directed “at the air” or at the handler and not toward their mother. All of the handled foals (IT) struggled during handling (attempting to get up) before lying motion- less with high muscle tone (Henry et al., 2009).

Six Months Old

Handled foals (IT) were observed on pasture with their mothers and the other mares and foals. Handled foals (IT) appeared more dependent on their mothers. They interacted more with their mothers than with the other foals and played less (especially social play). Handled foals (IT) also explored “new” objects in the paddocks less (such as an unfamiliar, motionless human) compared to control foals. Only three out of the nine handled foals (IT) approached the unfamiliar human, while all of the control foals approached and investigated the human. The observed differences between the handled foals (IT) and control foals involved social-emotional behaviors. Other behaviors (exploring, moving around, resting, self-grooming, etc.) did not differ from the control foals.

Seven Months Old (Weaning)

Following separation from their mothers, both control and handled foals (IT) experienced similar stress levels. Increased vocalizations and aggressiveness toward each other were observed in both groups, which indicated that the social stress of weaning was similar in both control and handled foals (IT). However, after the second day, the emotional reactions of the control foals decreased, while high levels of vocalization in the handled foals (IT) continued. Handled foals (IT) also engaged in less solitary or social play.

One Year Old

Both handled (IT) and control foals were separated and housed in same-sex groups. Most normal activities of the foals were not different. However, the experimental foals tended to withdraw socially, spend more time at greater distances from their peers, and exhibit more aggression. Control foals also displayed almost three times more friendly, positive gestures toward each other, while handled foals (IT) displayed more fighting, fleeing, or submissive behaviors. In this study, differences between the neonatal experiences of the foals revealed short-, medium-, and long-term effects of early experience on attachment and social competence later in life. As Henry et al. (2009) states, “These results underline the importance of this early stage for appropriate social development, despite later experience with peers.”

My Simple Summary

The study reviewed here shows that forcefully handling foals can have various effects on behavior, mostly negative. The negative effects of intensive handling may be more harmful in highly reactive breeds such as Arabians and Thoroughbreds or individuals within any breed with high hair whorls and a highly reactive nervous system. In any case, foals that are not handled may also present a problem. At some point, they need to be trained to accept handling for hoof care or health care. When these procedures become necessary, forcing foals may cause undue stress and influence the way they respond to handling in the future. A practical and easy way to teach foals to accept handling by people without making them fearful is needed.

In Part Four of this series, I introduce how I handled foals born on my ranch in Colorado over twenty years.

R.C. Miller (1991) Imprint Training of the newborn foal. A Western Horseman Book

Henry, S., Richard-Yris, M.A., Tordjman, S., Hausberger, M., 2009. Neonatal handling affects durably bonding and social development. PLoS One 4 (4), 19.

Henry, S., Hemery, D., Richard-Yris, M.A., Hausberger, M., 2005. Human mare relationships and behavior of foals towards humans. Appl. Anim. Behav. Sci. 93 (3), 341362.