Studies in restaurants show that the tips left by customers who pay their
bill in cash tend to be larger when the bill is presented on a tray that
bears a credit-card logo.
事實：餐廳付現金顧客，帳單盤上面有信用卡LOGO的，會付比較多小費
Consumer psychologists hypothesize that simply seeing a credit-card logo
makes many credit-card holders willing to spend more because it reminds them
that their spending power exceeds the cash they have immediately available.
詮釋/假說：看到LOGO

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