Are animal instincts and preferences based on some brain micro structures? I'm thinking about the mechanism by which an animal has built in preferences for some visual objects in the real world. The most well known example is the seagull chicks and pecking at a red dot or stripe:



I can think of other examples that expose preferences:


Human male preference for nubile females
Human baby preference for human face over a rock
Human observers being able to predict election results based solely on photos of candidates


It seems that in each case there's some very rapid analysis of visual features taking place, and in case of newborn babies, there's not enough time to be "taught" to perceive something specific. This makes me ask:

Are there any structures (adaptations) within the human brain which are responsible for our built in instincts and preferences?
There is the structure called the Fusiform-face area (FFA), which is located in the low tempero-parietal region. In human studies, the FFA has shown to highlight strongly when you look at a human face, as opposed to any other (inanimate) object. This is what the region got its name from. 

However, it is believed that the FFA is not necessarily a face area (See "Function and Controversy" on the Wiki page). Instead, researchers argue that the area is a visual expertise area. Where we, as humans, are experts in recognizing faces, zebras, for instance, are incredibly good at distinguishing the stripes of other zebras. 

This even goes for within-species differences. Western people that have never worked with Chinese symbols will show little to no activation in the FFA, whereas Chinese people that use it daily will show this activation. This would also explain cross-race recognition (thanks Josh) i.e. it is easier to distinguish people from the same race then someone from different races. 

With regard to your question about preferences: I don't know for sure. I have heard that people like what they know. That would imply that whatever the FFA is expert in, is more preferable to the person/animal. I have no reference, so if anyone does have some, I welcome you to edit my answer or post your own.