Supervisor:   Dr Siobhan Abeyesinghe

Department:  Pathobiology and Population Sciences

The 21.4 billion (FA0Stat 2017) domestic fowl worldwide hold huge global significance as a primary food source, but as ‘exploited’ animals with different in biology and behaviour to humans, low perceived individual intrinsic value. The recent Brexit and animal sentience debate highlights the need for increasing the evidence-base supporting capacity for subjective awareness and complex cognition; the debate on fowl sentience is likely to increase given the increasing human population and demand for low cost meat.

Inequity aversion (IA) is the aversive reaction of an individual to an unequal distribution of resources (Massen et al 2012), demonstrating recognition of ‘unfairness’. To date IA is associated with species that cooperate and form complex social relationships (e.g. primates, dogs, ravens) and is thought to be a mechanism by which cooperating individuals can avoid exploitation, and the root of an emergent sense of justice Chickens do not appear to form friendships (Abeyesinghe et al 2013), but do show some aspects of empathy towards offspring (Edgar et al 2011) and use social information about group members in social decision making (Nicol & Pope 1999; Hogue et al 1996). If IA were to be demonstrated in chickens it would suggest an earlier evolution of this trait than generally considered, and would be an important finding in the field of comparative cognition. This study will explore hens’ ability to recognise social inequity during reward acquisition.

Aim: To explore whether hens demonstrate IA aversion.


Focal birds will be slower and/or cease to work for their subsequent reward and show more behaviour associated with negative affect than control conditions (non-social non provision/unequal provision; equal provision of reward) if

  1. they do not receive a reward following observation of a companion receiving a reward for the same effort (reward absence);
  2. they receive a low value reward following observation of a companion receiving a high value reward for the same effort (reward inequity);
  3. they receive a reward following observation of a companion receiving an equal value reward forthe less effort (effort inequity).
Project Timeline
Month Task
1 Conduct a critical literature review on inequity aversion in animals


3 Eighteen naïve hens will be preference tested and pair matched for food preferences and estimated rank using comb size (O’Connor et al 2011). Nine pairs of hens will be simultaneously trained in transparent booths to peck a bell for food in turn, whilst able to see each other and subsequent rewards.
4 Hypotheses 1 & 2 will be tested using 7 treatment conditions experienced in a random order across days involving combinations of receipt/non receipt of rewards, receipt of unequal rewards and control for social context (e.g. Range et al 2009). Each bird will act as both a focal and a companion on different occasions.
5 Hypothesis 3 will be tested using the same hens with new conditions involving combinations of receipt of the same value reward for more (10 bell pecks) or less (bell peck) effort and non-social controls).
6 Video footage of trials will be analysed to score latencies to respond and frequencies of key behaviour & data analyzed to determine treatment effects. Hens re-homed.
9 Final write up
11 Submit dissertation
12 Viva

This is a full-time (12 month) project commencing in October 2018.

Project Costs - to be confirmed

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