Psychology Critical Review Essay
Ghirlanda, Jansson, and Enquist (2002) used both humans and chickens as participants. With the assumption that similar processes can develop in any nervous system, a comparison of these two species’ preferences to human faces was made, with the aim of determining whether human preferences arise from general properties of the nervous systems, or from face-specific adaptations. However, several methodological issues have been encountered and are discussed below.
In their design, they used a set of seven faces as stimuli. These were increasing in femininity, ranging from exaggerated male traits to exaggerated female traits.
Figure 1: Set of …show more content…
The results indicate that the last three faces from the set were pecked the most during the test trials, while the first three were pecked the least. Face three represents the rewarded face for chickens used in the training period, and the same sex average face for humans, while face five represents the unrewarded face for chickens, and the opposite sex face for humans (see Graph 1). The results can be interpreted as less pecking for the unrewarded faces, and more pecking for the rewarded faces for chickens, and lower ratings for the same sex and higher ratings for the opposite sex in humans. Having found almost identical behaviour in humans and chickens in response to the faces, the experimenters stand for the bias hypothesis, the fact that the receiver’s preferences are due to nervous system biases, which are similar in chickens and humans.
Graph 1 : Average human ratings and chicken pecks in response to the faces
An important problem is the difficulty of differentiating between the bias and mate-quality hypothesis given the methods used in the experiment. More specifically, is the exhibited preference by chickens and humans a result of more general mechanisms used in discrimination or recognition tasks, or is it a result of more complex mechanisms, which are