What is it about?
A key question when exploring cognitive processes that involve more than one stimulus is "how does the system cope with increased load"? That is, what happens when more stimuli are added? The capacity coefficient in the Systems Factorial Technology framework has provided a tool to answer that question for over 25 years. The measure contrasts response times when one and two items are displayed, respectively. The assumption is that we can directly compare the processing of the "target" stimulus that has been presented. We show here that when two stimuli could have ben presented, a decision that "there is only one stimulus" can alternately be framed as a decision that "at least one stimulus was not present". While seemingly a minor change in framing, this change violates key assumptions of the measure and essentially invalidates comparisons made using it. We provide empirical evidence from several studies that show our re-framed decision process is how participants generally make these decisions. We then develop an adapted task and corresponding mathematical capacity coefficient that overcomes these issues, and reccommend that future researchers implement this novel method.
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Why is it important?
For over 25 years researchers have relied on an assumption that we show to be incorrect. Our work highlights the importance of understanding the implications of assumptions we make in scientific work. More specifically, our work highlights the importance of "detecting absence" in cognitive processing, as a distinct process from "detecting stimuli".
Perspectives
This publication represents a challenge to an existing framework, and highlights the importance of developing a deep understanding of the statistical frameworks we use. These measures were used for 25 years without question, and now some of that research may need to be re-examined.
Zach Howard
University of Western Australia
Most, if not all models that attempt to predict or explain how mental workload affects efficiency as captured in response times, uses the same type of model structure and parameters whether the 'object' is a physical feature or stimulus or a blank (in vision, silence in the case of sound; and so on). Among a number of advances, this research reveals that 'absence' must be considered in it own right and may possess distinct processing characteristics from material stimuli.
James T. Townsend
Indiana University System
Read the Original
This page is a summary of: A show about nothing: No-signal processes in systems factorial technology., Psychological Review, January 2021, American Psychological Association (APA),
DOI: 10.1037/rev0000256.
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