An emotion as such tells you nothing about reality, beyond the fact that something makes you feel something. Without a ruthlessly honest commitment to introspection—to the conceptual identification of your inner states—you will not discover what you feel, what arouses the feeling, and whether your feeling is an appropriate response to the facts of reality, or a mistaken response, or a vicious illusion produced by years of self-deception....Where is Rand's evidence for this view? Again, we have nothing -- merely her own say-so. In Objectivism, emotions are equated with mere "whims"; to allow one's judgment to be affected by emotions is tantamount to committing the horrible crime of "whim worshipping." This, of course, is an argument ad hominem with no scientific standing whatsoever.
Cognitive science has discovered that emotions play an important role in decision making:
Recent research suggests that emotions are just as influential as cognitive processes when it comes to decision making. This is interesting because emotions are often considered irrational occurrences that may distort reasoning. According to Sayegh, the conventional way of thinking about decision making is to banish emotion from its decisions entirely. According to them, the decision makers should act using a “cool head” where decisions should come only from rational and cognitive processes to obtain the best results. The implications of emotions during decision making processes have only recently been discussed in some detail. With the growing body of knowledge on emotions in decision making, researchers have proposed various theories to help further our understanding of what influences the decisions that we make.
One of the most important theories illustrating the role that emotions play in decision making is the Somatic Marker Hypothesis:
The somatic marker hypothesis is a very relevant theory when discussing emotions in decision making. It states that bioregulatory signals such as feelings and emotions provide the principal guide for decisions where individuals, when dealing with a judgement, will assess the severity of the outcomes, their probability of occurrence and their emotional quality to provide their decision. According to Dunn,“the somatic marker hypothesis proposes that ‘somatic marker’ biasing signals from the body are represented and regulated in the emotion circuitry of the brain, particularly the ventromedial prefrontal cortex (VMPFC), to help regulate decision-making in situations of complexity and uncertainty”. Therefore, in situations of complexity and uncertainty, the marker signals allow the brain to recognise the situation and respond quickly.
As mentioned earlier, there is an intimate connection between emotion and cognition in practical decision making. Damasio used somatic marker hypothesis to explain how emotions are biologically indispensable to decisions. He suggested that when choosing between options that differ in relative risk, a somatic marker (for example, a “gut feeling”) feeds back to the brain and influences cognitive appraisal. Thus emotions often unwittingly form the basis of many of our decisions and the conventional belief that cognitive processes alone run our decision making processes has been disregarded. It is in fact an interplay between emotions and cognition that helps us during decision making processes.
Now whether right or wrong, at least the Somatic Marker Hypothesis has a body solid evidence that can be placed in it's favor. For example, it is found that people who, through brain damage to the VMPFC, suffer from impaired emotional faculties are incapable of making the simplest decisions. One patient was unable to choose an appointment time with his neurologist because he gave countless arguments for every time that was proposed.
If Objectivists wish their view of the role of emotions in cognition to be taken seriously, they need to (1) provide scientific evidence on behalf of their view, and (2) explain why the evidence supporting the Somatic Marker Hypothesis is not inconsistent with Rand's assertions about emotion.