The Effect of Previous Experience Over Control of Access to Food and Light on the Level of Frustration-Induced Aggression in the Domestic Hen


M. J. Haskell, Animal Biology Division, SAC, Bush Estate, Penicuik, Midlothian EH26 0PH, UK. E-mail:


Animals have been shown to respond to frustration with increased aggression and activity. Aversive environmental conditions are also known to affect reaction to frustrating events. One pertinent and aversive environmental factor that has been shown to affect aggression is exposure to uncontrollable rewards and punishments. Although used largely in experimental contexts, this situation is similar to that found in modern intensive farming systems, where environmental and social conditions are largely controlled. The aim of this experiment was to determine if previous experience of lack of control influences the expression of aggression and frustration in domestic hens (Gallus gallus). The two treatment groups of hens used had previously been exposed to control (C) or lack of control (LC) over access to food and light, additional to a restricted regime, continuously for 9 wk. Dominant-subordinate pairs of birds were tested under water deprivation. After training, the pairs were tested for two rotations of 4:3 d of free access to the water followed by a thwarting trial. Dominant birds showed significantly more aggression in thwarting trials compared with non-thwarting trials. While there was no main effect of treatment on the aggression shown during non-thwarting trials, an interaction between treatment and trial type (thwarting and non-thwarting) indicated that the LC group showed a smaller rise in aggression from non-thwarting to thwarting trials than the C birds did. However, there was a great deal of variation shown between birds in the amount of aggression. As the home pen conditions were set up to model those found in commercial practice, this possibility that a lack of control leads to some degree of learned helplessness in intensively farmed animals needs to be considered further as it has serious negative implications for animal welfare.