The Experiment

By far the most common approach to understanding cognition is through the experiment. In an experiment, a researchers manipulates one or more independent variables (sometimes these are referred to as conditions) and measures how this manipulation changes something in the environment (called the dependent variable). If the experiment is designed in the right way (although a perfect design is rarely, if ever, attainable), researchers can conclude that changes in our dependent variable were caused by manipulations of the independent variable.

The experiment has proven to be a very powerful method in understanding cognition. The experiment has a distinct advantage in that it allows for much more control over the other methods. Oftentimes (although not always) experiments are performed in the laboratory, where factors in the experiment can be precisely controlled. In fact, control is one of the distinguishing features of the experiment. When designing the study, the researcher wants to control as many things as possible.  This control allows for the strongest conclusions to be drawn.

The experiment has a long history in cognitive psychology. In fact, the experiment has been used since the dawn of psychology to examine psychological phenomena. Gustav Fechner (discussed earlier in this lesson) developed experimental methods to study the relationship between the environment and our perceptual experiences. He carefully studied the relationship between sensory experience and the strength of stimuli in the environment. One of the methods he developed, the method of constant stimuli, is frequently used today. The method of constant stimuli can be used in a variety of designs and is particularly good at measuring thresholds, which are the minimum amounts of energy required to detect a stimulus is present or to the minimum difference required to detect a difference between two stimuli. The practice CogLab assignment this week involves a study that uses the method of constant stimuli to measure the strength of the Müller-Lyer illusion (see the Assignments page in this lesson).

Naturalistic Observations

Naturalistic observations consist of an observer watching people interact with their environment in real-life contexts. For example, researchers may be interested in how users interact with a new self-checkout machine at the local grocery store. (Yes, this is one of the things that cognitive psychologists study—the design of machines and interfaces to allow for efficient cognitive use.) A researcher may watch customers as they scan, pay for, and bag their goods. 

The advantage of naturalistic observations is that they represent what goes on in the real world (unlike traditional experiments completed in the laboratory). Also, researchers can study how cognitive processes work in natural settings. For example, researchers may look at the flexibility of the processes, the complexity of the behaviors, and how they are affected by changes in the environment. 

The disadvantage of naturalistic observations is that the researcher loses control over the environment. It becomes much more difficult to isolate causes and effects. For example, in the self-checkout lane, people may have varying amounts of experience, the machine could be slow that day, or any other of a number of factors could influence how the users interact with the machine.

Controlled Observations

Controlled observations, as the name suggests, allows the researchers to establish more control over the observations. For example, participants may be selected on the basis of some characteristic, different instructions may be provided for certain participants, or certain information may be displayed for some participants. The observations are often still conducted in the real world, but the researcher tries to influence the process. This influence allows the researcher to draw stronger conclusions and test a certain hypothesis. Typically, the amount of control afforded to the researcher in a controlled observation is less than what we would see in a traditional experiment in the laboratory.

Neural Underpinnings

With the technological advances in the past 50–60 years, cognitive psychologists can now look inside the brain (to a certain degree) while a person is alive and well. Much of the work in cognitive neuroscience focuses on the study of the brain and the neural underpinnings of our behavior. For example, neuroscientists might look for areas of the brain that are involved with memory or speech or discover which neurons are active when we make decisions. The discoveries from cognitive neuroscience have revolutionized our understanding of cognitive psychology. We won't spend much time talking about these methods in this lesson; the entirety of Lesson 2 is devoted to cognitive neuroscience.