Designing a product or service takes a lot of thought and effort. In order to make a successful product or service we must understand how the customer will interact with what we make and their possible reactions to our product/service and/or interface. Using psychology to understand how and why people act in a given situation and then recreating that situation either in a product; such as "Facebook" or "LinkedIn" is one way to implement psychology in design. This approach uses a broader scope on design, which includes the product or service being offered. The other approach has a more limited scope involved and only includes the choices made by the designer that dictates functionality. These choices are based on things such as aesthetics, colors, button shapes/textures, layout and typography. Obviously these are not the only concerns or applications when using psychology and design together, but they are certainly things to be taken into consideration.
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Examining psychology and how it effects the design process is very important to both the user and the designer. The user needs to have a successful and pleasant experience with the product/service and the design ensures that this happens. Incorporating psychologically motivated design decisions can be a successful way to persuade or direct users towards a specific or non-specific action. An example of this implicit influence would be the use of "Hick's Law". "Hick's Law" or the "Hick-Hyman Law" is a model of human-computer interaction that describes the time it takes for a user to make a decision as a function of the possible choices he or she has."(Wikipedia)
T = blog2(n + 1)
Above: Hick's Law Equation
So overall the psychological influence in design is a very important factor to be taken into account when designing products, services and the aesthetics of a system. Neglecting the the implicit and explicit psychological influences can and will most likely hinder how you want the user to interact with what product/service you are providing. In all when designing, it is recommended to do the proper research on who your target user(s) is/are and how you want them to interact with the product/service being offered. Investing the time into these design decisions and research will pay off for anyone willing to implement them into their products/services and digital interfaces.