When someone *desires* an income increase, he/she (let's say "it" in order to be politically correct) will welcome any change in that direction. An orthogonal change will be first seen as a nuissance, before being evaluated and re-classified as something good or bad (perhaps it stands in the way of something else we wanted or the opposite) or just a nuissance.
Any change in the opposite direction will be seen as a menace and cause anguish.
I've seen this happen again and again, on myself and on others near me.
As for why I believe we are hardwired to avoid change, I believe it has an evolutionary origin.
Imagine a primitive man who happened to found a lake full of fish. He went out of the jungle for there were now too many predators (an involuntary change opposite to what he desired), and then spent several days figuring out how to fish (while fasting, must be said).
Having just learn, he would desire either the fish or the lake to become larger so as to have more food easily available. He will welcome an unexpected flood or a sudden increase in waterlevel - it's in the direction he desires (until a week later he finds the flood also made several good resting places to dissappear under water, then he'll make a choice to reclassify floods as good, bad or a fair tradeoff between good shelter and good food)
But he will feel anger/anguish if the lake suddenly dries up: he will have to look for a new food source (read: spent energy while starving for a week or 2) and let's hope it's easily eadible - if it's something that has to be cooked before eaten, well, our poor primitive man can easily go to a better world. Or he may eat a poisonous fruit/fungus/fish/something believing it's eadible. Either way, he is just spending energy and time, trying just to survive (and he has no way to be sure he will indeed survive in the end) whereas in the previous situation he was able to get his living, knew how to make his living, and was sure that if things didn't change he would continue surviving.
If he happens to find another lake, and alongside it a new potential source of food, what will he choose? Obviously the lake. He's got no energy nor time to spend looking for a new energy source when he knows perfectly how to take advantage of this one. Perhaps in 2 or 3 weeks, once he's rested, he will give it a try. But not now.
The same happens if this primitive man believes there's a slight probability of finding a lake - he'll prefer to bet on the lake rather than attempting to exploit a new food source. If he does find a new lake, bingo! He needs spend no more energy/time, he'll just eat. If he doesn't, well - he will be obligated to try the new source (which will make him feel sad and threatened).
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