Making assumptions may make us skip over important information we may need to solve a problem. This can happen in a variety of problems, especially when they involve people. We carry around many preconceived notions about how people and our society work. If we have a problem understanding a certain phenomena in society, it may be due to these kinds of assumptions. For instance, patriarchal society once widely assumed that women were destined for housework and many people didn't understand why women were so happy. They attributed it to their "biology". Instead, it's better understood that women desire just as much as men to participate in and feel like they belong in their society. 

The economist Herbert Simon noted that people very often do not make rational decisions. This is primarily due to the fact that it is difficult to simultaneously evaluate all possible options and so they tend to only focus on a few aspects of the available options. For instance, some people may be overly focused on what they'll lose in a certain options instead of how much they have to gain.

All of these are fallacies that impede one's ability to make decisions based on accurate reasons. The tendency to ignore base rates involves inaccurate correlation rates. For instance, if a person sees a man with motorcycle related tattoos they are likely to think he is a motorcycle owner. Yet they ignore the fact that the large majority of Americans are car-owners. The gambler's fallacy is summed up by the phrase "I'm due for a win!" Minimizing risk involves making a decision because the option is presented in positive terms. Overestimation of the improbable is when a person thinks the chances of an actually rare event are higher than they are.

Functional fixedness is a tendency to only think of an object's most common use when presented with a problem. For instance, if you are trying to open up an old-fashioned Coke and need a bottle-opener you may be so focused on finding a bottle-opener as opposed to using your keys. Your keys would work just as well, but because you are so focused on using it to open the door you don't think of its alternative use. 

Researchers have identified several mental obstacles to our problem solving/reasoning processes. Functional fixedness, mental set, and making assumptions, and irrelevant information are just some of many. Although their precise definitions won't be defined here, the commonality they share is a misdirection in focus and to an extent being stuck on what has worked in the past.

A "mental set" is an obstacle to problem solving which involves fixating only on solutions that have worked in the past. For instance, someone who knows that yelling and throwing a fit has gotten them what they wanted might only use this solution to get they want in the present. Instead, it might be more effective to think of a new solution.

Decision-making involves weighing alternatives and choosing between them. The other answers are a part of decision making but are too specific to the methods for our decision making processes. For instance, it isn't just risky decisions that involve weighing alternatives and choosing between them, but all decisions. The other answers are strategies for how we weigh the alternatives at hand. 

Additive strategies are commonly used when people are making decisions about their preferences. When using an additive strategy, a person lists the traits of each potential choice, weights them according to importance, adds them up, and determines which one is more appealing based on the result. Another common strategy is a strategy of elimination, which will not be discussed in detail here.

This is an elimination strategy. An elimination strategy is a decision making strategy where one sets a certain criteria and any options that do not meet this criteria will be automatically be eliminated. Although John deciding where to eat is certainly a form of judgment and cognition, these answers aren't sufficient because they are not as specific to what this process was. An additive strategy is a different type of process all together.

Functional fixedness is a cognitive bias that limits the way a person thinks about an object, restricting his or her view of that object’s uses to the “traditional” or typical uses of that object. The example with Joanne is the best choice, as it reflects functional fixedness restricting her view of the staple remover. She is probably used to using the staple remover to remove staples, so when she realized she could not open the keychain ring with her nails, she felt stuck. She did not think of being able to use the staple remover to hold open the keychain ring.