Chapter 13: Testing Protocols

Psychophysiological Tests
Synchronization to Visual and Auditory sequence
Stroop Test
P300 Test
Virtual Reality Implementations
Challenge and Threat
Physiologically Mediated Design Assistance
Emotional Dimension
Circumplex Model of Affect
Physiological Data Synchronized to Video
Historical Methods

Psychophysiological Tests

Indicators of sympathetic ANS activity include cardiac pre-ejection period (PEP) and electrodermal activity (EDA). PEP is the time period from the start of ventricular electrical stimulation to the opening of the aortic valve. Indicators of parasympathetic ANS activity include respiratory sinus arrhythmia. Sympathetic and parasympathetic ANS activity do not always operate in a reciprocal manner. Simultaneous activation and inhibition are possible.

EDA

EDA has two subtypes: skin conductance level (SCL) and skin conductance response (SCR). The SCL, also called “tonic skin conductance”, is a measure of general arousal which decreases with relaxation and increases with alertness. The SCR, also called “phasic skin conductance” is produced in response to a stimulus. The SCR varies in amplitude depending on the nature of the stimulus characteristics.

Respiration

Respiratory activity is subject to both conscious and unconscious control and variations in respiratory activity are associated with changes in emotional state. Respiration also affects measures of other physiological activity, including EDA and HRV. Even though respiration is subject to conscious control, under longer term basal conditions, respiratory activity has a typically consistent pattern.

Synchronization to Visual and Auditory Sequence

Visual and auditory stimulation is often employed in psychophysiological research. Typically, a computer is used as the stimuli generation system, via application software (SuperLab, EPrime, etc.) and an alternate computer is used as the physiological data acquisition platform. Furthermore, a direct, high level, digital-marking interface is established between the stimuli generation computer and physiological data collection platform. This interface allows for synchronization between the systems. When a specific auditory or visual stimulus is presented, the physiological data collection platform receives a simultaneous digital signal indication (via digital pulse or level change) that marks the physiological record as to the time of the stimulus.

Stroop Test

This test establishes conditions where there is a mismatch between colors and words that are presented to a subject. In the case of the original test, the words naming a color might be mismatched to the color of that word. The subject is asked to identify the proper color of the word, despite what color the word names.

Automaticity Theory

This theory proposes that color recognition is not an automatic process, so there is a delayed response when the subject attempts to identify color. Word recognition is an automatic process, meaning that reading does not require much conscious effort. Alternatively, naming colors requires more conscious effort than reading.

Processing Speed Theory

This theory proposes that the act of word recognition is significantly faster than that of color recognition. The word data arrives at the decision point before the color data. When the task is to identify the word color, interference results because of later impact of the conflicting color data. Alternatively, when the task is to identify the word, the decision can be made before the impact of the conflicting color data.

Selective Attention Theory

This theory proposes that the act of color recognition requires more attention than the act of recognizing a word. The task interference might be a consequence of attention-related resource allocation to the acts. Alternatively, the interference might be a result of increased attention to restraining distracting input.

Parallel Distributed Processing Theory

This theory proposes that different recognition tasks employ different neuronal pathways and processing steps. Automaticity increases with the strength of the pathway, not the speed of the pathway. Word recognition is a strong pathway. Color recognition is a weak pathway. If the two pathways are simultaneously active and the pathway leading to the response is stronger (word recognition) then no interference occurs. Alternatively, if the pathway leading to the response is weaker (color recognition) then interference occurs.

P300 Test

The P300 has two components: the P3a and the P3b. Both the P3a and P3b are time-averaged evoked responses, known as event related potentials (ERPs). Both the P3a and P3b are skin surface recorded, positive-going, neuronal potentials measured on the scalp. The P3a has a maximum amplitude on electrode sites over the frontal lobes. The P3b has a maximum amplitude on electrode sites over the parietal lobes. P3a and P3b measurement electrode sites are typically referenced to the mastoid or earlobe on that same side of the head. The P3a will occur about 270ms after the stimulus. The P3b will occur about 300ms after the stimulus. The P3a is linked to attention and orienting. The P3b is linked to the occurrence of improbable events.

Virtual Reality Implementations

Virtual reality platforms provide controlled and replicable experimental setups that allow computer-based manipulation of the environment and social interaction via avatars. Scenarios can be constructed that would be impossible or prohibitively expensive in the real world. It’s possible to synchronize virtual events with physiological data from a measurement system. Feedback loops can be designed to change the virtual world, in real time, based on the subject’s physiological state.

Challenge and Threat

Motivational state is based on the concept of core relational themes, called “challenge” and “threat”. Motivational state is indexed by specific, bodily-expressed, physiological states that can easily be measured. During the course of living, humans respond to environmental stimulus as a combination of challenge and threat. A challenge response is similar to an aerobic physiological response, and involves an increase in heart rate and cardiac output and a decrease in vascular resistance. A threat response is characterized by an increase in heart rate, blood pressure and an increase or little change in vascular resistance and a decrease or no change in stroke volume.

Physiologically Mediated Design Assistance

Human-sourced activity such as the physiological signals manifested by the heart, skeletal muscle, neuronal activity of the brain, eye movements, skin conductance or pulse are viable input data sources for computers and provide a wealth of information not readily available via alternate means. Consider the promise of computer interfaces that are capable of discerning one’s emotional dimension and motivational state for the purposes of enhancing and improving the creative design process and associated results. The realization of “emotional – motivational state resonance” between the designer and computer application could result in rapidly obtained design results that match the designer’s objectives. Such methodology could also be applied to design recipients to feed data back to the designer for inclusion into the design process.

Emotional Dimension

Circumplex Model of Affect

The Circumplex Model of Affect is described by the behavior of two independent neurophysiological systems, the arousal and valence systems. Affective states are a function of these two systems. The circumplex model is two-dimensional, with arousal and valence defined as orthogonal (perpendicular) axes. The arousal axis, plotted vertically, ranges from zero arousal to high arousal. The valence axis, plotted horizontally, ranges from negative to positive.

Physiological Data Synchronized to Video

Synchronized video coupled to simultaneously-recorded physiological variables can help lead to better understanding of responses. Video signals can be simultaneously collected with other types of time-series data, such as biopotential data (ECG, EEG, EMG, or EOG) or transducer data (electrodermal activity, force, pressure, temperature, accelerometer, goniometer, strain, etc.). A key issue when performing simultaneous recording of physiological data and video data is synchronization between the two streams of data. Video data is two-dimensional as a function of time. Physiological data is uni-dimensional as a function of time. Accordingly, the two streams of data-types are typically incompatible when using a single data acquisition system. However separate recording systems can be successfully used if they are linked using a periodic timing signal. In this situation, timing resolution can usually be maintained to the period of of one video frame (1/15 – 1/100 of a second).

Historical Methods

All physiological recording investigations are based on the premise of stimulus and response. The subject is being subjected to certain environmental conditions, intentionally or not, and there are related physiological responses. Historically, simple variations in environmental conditions were employed as stimulation sources, such as bursts of light or sound. Slightly more complicated methods, such as changing temperature or physical pressure, were commonly used. Coincident with more sophisticated delivery systems, varying electrical stimulation was increasingly utilized. Computer-based stimuli-generation systems can effect simultaneous delivery of all previous methods, including detailed audio and visual stimuli. The most evolved stimuli-generation systems are presently organized around virtual reality environments. These environments can be designed to be large volumes, to accommodate many people (such as UCSB’s Allosphere), or personally-worn virtual reality headsets (such as Occulus’ Rift).