Not everyone receiving a cash gifts want to make a 20% downpayment, though. Cash gifts are also allowed for low-downpayment mortgages including the FHA purchase mortgage, which requires a 3.5% downpayment; and the Conventional 97 mortgage from Fannie Mae and Freddie Mac which requires just 3% down.
Hardwiring Happiness is a psychology/but actually mostly a self-help book. I obviously went into it with expectations that weren't met, but it's not all bad. I did get the psychological research that I wanted and more.
In his 2002 book Authentic Happiness, Seligman proposed three 'orientations' of being happy, or three kinds of happiness: 1) Pleasure. An individual leading a life of pleasure can be seen as maximizing positive emotions, and minimizing negative emotions.