Irrationality refers to actions, decisions or beliefs that are not based on logical or rational reasons, but are influenced by emotions, prejudices, instinctive reactions or other factors. Irrationality can lead people to make decisions that are not in line with their interests or goals and may even be harmful.

In neuromarketing, the irrationality of human behaviour is often used to influence purchasing decisions. By using emotional or psychological triggers, designers and marketers can attract the customer's attention and motivate them to take an action. An example of this is the use of colours or images that trigger positive emotions to arouse the customer's interest and increase their willingness to buy.

However, it is important to note that the use of irrationality in neuromarketing should be ethical and responsible and that customers should still have the opportunity to make informed decisions. Designers and marketers should ensure that their advertising strategies are fair and transparent and that customers have the opportunity to receive all relevant information to make an informed decision.