Naïve diversification is a choice heuristic (also known as “diversification heuristic”).
Its first demonstration was made by Itamar Simonson in marketing in the context of consumption decisions by individuals. It was subsequently shown in the context of economic and financial decisions. Simonson showed that when people have to make simultaneous choice (e.g. choose now which of six snacks to consume in the next three weeks), they tend to seek more variety (e.g., pick more kinds of snacks) than when they make sequential choices (e.g., choose once a week which of six snacks to consume that week for three weeks). That is, when asked to make several choices at once, people tend to diversify more than when making the same type of decision sequentially.
Subsequent research replicated the effect using a field experiment: on Halloween night, young trick-or-treaters were required to make a simultaneous or subsequent choice between the candies they received. The results showed a strong diversification bias when choices had to be made simultaneously, but not when they were made sequentially.