What can interfere with solving the two-string problem?

The correct choice highlights the importance of how our perceptions and mental frameworks can impact problem-solving. In the context of the two-string problem, individuals are often presented with two strings that are separated by a distance, and the goal is to tie them together. A common obstruction in solving this problem is a fixed perception regarding the conventional uses of the objects provided, such as thinking that a hammer can only be used to strike a nail. This kind of mental set can prevent individuals from seeing alternative uses for the tools at their disposal, such as using the hammer to swing one string towards the other.

When individuals adhere too rigidly to established functions or uses of objects, they may overlook innovative or unconventional approaches necessary to find a solution. This cognitive rigidity is what primarily interferes with finding a successful answer to the two-string problem, highlighting the broader concept in cognitive psychology of functional fixedness.