I would say affects, because effects is used in a different form like ' the effects of x on 500000 Australians' and affects is used like ' x affects 500000 Australians'
The blind men and the elephant describe a situation when many men have different opinions, but none of them are wrong; they just describe parts of the whole.
It shows that many different psychological theories
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contribute value: they might be contradicting but in fact they all describe different aspects of the same</span>