Methods and Measures

In the lab, we use several different methods and measures to get at the questions we want to explore. Many, if not all, of these methods are indirect in that they get around explicitly asking for answers. These include things like reaction time tasks, mouse-tracking, eye-tracking, facial coding, and psychophysiological measures. Some of these are described in more detail below.


Reaction Time

Reaction time tasks typically involve measuring the speed at which people respond to different classes of stimuli. In doing so, these measures indicate the strength of a person’s association (i.e., their attitude) between mental constructs in memory. There are several types of these measures, including but not limited to:(1) Implicit Association Tests, (2) Priming Tasks of various sorts, (3) Lexical Decision Tasks, (4) Weapons/Shooter Tasks, (5) Affect Misattribution Procedures, and (6) Visual Search Tasks.

For further reading see: Fazio, R., & Olson, M. (2003). Implicit Measures in Social Cognition Research: Their Meaning and Use. Annual Review of Psychology, 54, 297-327.

Physiological Measures

Physiological measures involve observing and recording a response emanating from within the body that reflects some type of physical reaction. These measures are derived from the measurable properties and functions of human biology. Natively, these measures are informative as health markers; but, when combined with social psychological, and behavioral measures, they can be used to discriminate between responses to different types or classes of stimuli.

Below I describe a couple of the measures used in the lab, as well as some others.

Skin conductance/electrodermal activity (SCR/EDA) is a method for measuring the electrical conductance of the skin which is used as an index of physiological arousal. Typically, people show increased SCRs to any highly arousing stimulus, whether it be positive or negative in valence.

Facial electromyography (fEMG) in combination with noise-blasts can be used as a noninvasive way to index central nervous system activity. The so called startle-eyeblink paradigm measures blink amplitude by recording electrical potential generated by the orbicularis oculi muscle responsible for closing the eye. As an index of amygdala activation (i.e., underlying autonomic activation of unique evaluations), the startle response distinguishes reactions to different classes of stimuli.

There are other measures, like electrocardiogram (ECG) and heart-rate variability (HRV) that take advantage of the hearts natural responses to index how people react to stimuli, electroencephalography (EEG), which reflect cortical activity that indexes responses in certain surface brain regions, and even biochemical/genetic markers that give insight into individual difference predispositions and responses.

Mouse Tracking

In Mouse tracking studies, participants are exposed to visual stimuli and instructed to categorize a stimulus utilizing a computer mouse. During this categorization, behavior outcomes, errors, as well as reaction times all produce information valuable in understanding online cognition. As physical movement often functions parallel in response to cognition, one may understand mouse tracking as “a way to visualize the path of human thought” by capturing in real-time the behavioral outcome of processes occurring within the human mind.

Mouse-tracking records x-, y- coordinates of motion when participants choose between response alternatives and provides information, beyond total response time, about the influence of competing alternatives during the decision process. These responses are captured by metrics like Area Under the Curve (AUC), which captures the sum of competition engendered by the distractor across the entire time-course of response.

In addition to the native measures typically included in mouse-tracking packages, I have worked to adapt a growth-curve modeling method often utilized in bacterial growth sciences to demarcate when in time the decision process began. Through this process, I calculate the lag time, or the point in time when the participant begins moving relatively closer to the target than the distractor. The lag time reflects when the initial automatic response is either or when the initial “incorrect” response is weakened to the point of being overcome. While, AUC plays out over the entire length of the response process and is likely susceptible to other influences (i.e., attempts at control), the lag time reflects initiation of movement toward the correct response as reflecting when in time the decision is made.

Eye Tracking

eyetrackinganimated_origEye movement is an action that often occurs involuntarily in response to outside stimuli. Such movements are the result of an interaction between perceptual and cognitive processes. Tracking the movement and fixation of the eyes following the presentation of a stimulus allows researchers to index various levels of cognition and track attentional responses to different types of stimuli. Eye tracking can act both diagnostically by quantifying a participant’s visual processes, or interactively, responding to the actions of the participant.

In quantification, we look at things like first-movement, number of fixations, total time spent looking at objects, and where in a scene people actually look. All of these give us insight into how people are processing and responding to a stimulus. In responding, we can actually build logic into the experiment such that what the participant experiences next is dependent on their previous eye movements. In doing so, we can build a flexible and ecologically valid experience.

Facial Coding

peg_2-2019As social beings, humans often portray information (e.g., emotion, motivation) through facial muscle movement and facial expressions. Facial Coding is an anatomically derived method for discerning and quantifying various large and minute facial muscle movements. When paired with a stimulus, facial coding quantifies movements of muscles within the face to index emotion or attitude toward a stimulus. Originally, this method involved manually coding video of participants responding to stimuli (and it often still does for convergent validity). But now we typically use facial coding software to makes the process much quicker and allow us to code many more participants worth of data. Facial coding grants insight into the motivational or dispositional response to whatever the participant is viewing and can be a unique tool for exploring people’s automatic and nonconscious responses.