The Objectivist ethics does not look favorably on jealousy. The judgments that a jealous person makes of a rival are far from being models of epistemic objectivity, and jealous feelings are regarded as a sure sign of low self-esteem. In Ayn Rand’s fiction—most memorably, in Part II, Chapter IX of Atlas Shrugged—jealousy openly expressed is not just a badge of weakness but a near-guarantee of loss or rejection.
In the context of Rand's theory of emotions, jealousy must be regarded as a product of value premises, rather than an innate predisposition triggered by specific circumstances. Did Rand present any evidence that jealousy was an acquired rather than an innate predisposition? No, of course not. Does such evidence that exists on the question tend to support Rand's view? No, it does not.
Jealousy is very commonly observed, widespread emotion. It exists in all cultures and affects nearly everyone (though some people may be more prone to it than others). Experiments show that it can easily be triggered, even people who don't regard themselves as the "jealous type."
David Desteno and Piercarlo Valdesolo decided to test how easily jealousy can be triggered in individuals:
We orchestrated a complex social reaction that stimulated ... how jealousy naturally occurs in the real world: a relationship starts, it's threatened by a rival, and then it actually dissolves due to the rival.... Basically, the unknowing participant was being set up for the ultimate brush-off. Why would we put people through this? Because, harsh as it might sound, it is the most valid method of studying how jealousy works in everyday social interactions. [Out of Character, 85]
The initial experiment worked as follows. Carlo Valdesolo pretended to a be a participant in a psychological experiment which involved answering trivial questions. He pairs up with a female participant and immediately begins flirting with her. A little later, another female enters the room, allegedly to take part in the experiment. Carlo begins flirting with the new female "rival," until he suggests to her, "Why don't we pair up," leaving the other female participant, the true subject of the experiment, to stew in her own juices.
What was most interesting to us about [the results of the experiment] was that such a small slight could so drastically affect people's sense of self and emotional state. If you look at the author photo on the jacket of this book, you might be skeptical -- that guy made people jealous?... Yeah, that's right. And not just a little jealous, either. Some participants' faces quite literally dropped when Carlo threw them over for the other woman. Others let out audible gasps. One participant found the rejection so unbearable, she repeatedly shushed Carlo and the rival as they worked on their tasks, angrily sneering, "I can still hear you" when they continued to joke and giggle together on the other side of the room divider. All of which speaks to the power of jealousy and how quickly it can rear its ugly head to protect even the potential for a relationship. [86-87]
Valdesolo and Desteno next devised an additional experiment to test what it would take for a seemingly normal person to become jealous enough to actually inflict harm:
Here's where things got even more interesting. After participants got the brush-off from Carlo, ... they were told that there was one last part of the experiment to complete.... All participants had previously filled out a questionnaire on which they'd had to rate how much they liked of disliked certain flavors (e.g., sweet, sour, spicy). For the final phase of the experiment, our real participant was presented with a box that contained the taste preferences questionnaires of both the snubber (Carlo) and the rival, several foods chosen because they were supposedly the strongest versions of those flavors we could think of, ... and small plastic cups. We next told the participant that we needed the others in the study to actually taste the substances and rate their preferences, but that because we needed to be blind to who ate what before taking these assessments, we needed the participant to measure out "randomly" assigned substance for us. It was further made clear to the participant that she was free to dole out as much or as little of the substance as she felt was appropriate, and that the other two (the snubber and the rival) would have to consume every last drop.
Then we left the room and gave the participant some time to read the questionnaires (who could resist?) and prepare the samples. And when she read the questionnaires, what did she see? That these other two hated spicy food (naturally, we'd rigged the questionnaire to read this way), which was what she'd been randomly assigned to give them. So now she was faced with a difficult decision: how much extra-strong hot sauce did she want to give this sleazy, no-good jerk and his floozy? Turns out it wasn't that difficult a decision after all. The jealous participants loaded up the sample cups with more painful stuff, filling them with significantly more than those in the control condition did. As it turned out, how much hot sauce they poured was directly predicted by how jealous they felt. [88-89]
Now if the Objectivist theory of emotions were correct, we would not expect to see such a unanimity in the behavior of the jealous subjects. After all, jealousy is not an emotion that is well thought of. If emotions are integrated value premises, how does one explain the near unanimity of value a premise which tends to be despised in the culture? If jealousy is not innate, but a product of the culturally predominant philosophy, how does one explain the general disparagement of jealousy? In the light of the Objectivist view of emotions, isn't it odd that individuals should have one type of emotional reaction when they speak and think, and another when they act? These inconsistencies aren't noticed by Objectivists, because their views on these matters are determined, not by fact and logic, but merely by sentiment and Rand idolatry. Doctrines which trace all human emotions to culture and/or ideas cannot explain widespread inconsistencies between rhetoric and behavior. If there are no innate predispositions, it makes no sense at all for the culture to influence nearly everyone in one direction when it comes to voicing one's feelings and opinions, and the exact opposite direction when it comes to behavior and conduct.