Fear inducing stimuli are common in modern intensive husbandry systems. It is probable that a principal source of fear is the humans who work with the animals and who, by necessity, have close contact with the animals when carrying out routine husbandry practices.

Signals generated by the stockman, either intentionally or unintentionally, may be perceived by the pig as threatening. There is growing evidence that the complex behavioural relationships between stockmen and their charges can profoundly influence productivity. Seabrook, (1985) found that the personality of the stockman influenced the behaviour and performance of dairy cows. Similarly, Hemsworth et al., (1981) found that on those farms where sows displayed increased avoidance behaviour to the experimenter, the number of piglets born per sow was depressed. In a subsequent study it was found that those pigs which were highly fearful of humans as a result of being aversively handled, exhibited impaired reproductive performance and elevated basal Cortisol levels.