The upper portion, for gains, has the same shape as the usual utility of wealth function, capturing the idea of diminishing sensitivity. But notice that the loss function captures diminishing sensitivity also. The difference between losing $10 and $20 feels much bigger than the difference between losing $1,300 and $1,310. This is different from the standard model, because starting from a given wealth level in figure 1, losses are captured by moving down the utility of wealth line, meaning that each loss gets increasingly painful.
