A perfect illustration of what people do when confronted with the rotting-head of 'Modern Art'. You are either the child, bemused by it all; or the daddy, enthusiastic and knowledgable.
I reckon most are the uncomprehending child and rely upon the few daddy's amongst us to explain it for them. The more you look into the context of a Modern Art piece and the reason for it being; the more meaningful and clearer it becomes.
But in the case of some, like David Shrigley's drawings, i'd say it's best to revert back to the humour of your childhood :)