Academic journal article Canadian Journal of Experimental Psychology

A Timely Reminder about Stimulus Display Times and Other Presentation Parameters on CRTs and Newer Technologies

Academic journal article Canadian Journal of Experimental Psychology

A Timely Reminder about Stimulus Display Times and Other Presentation Parameters on CRTs and Newer Technologies

Article excerpt

"Don't trust the computer or the program."

-Saul Sternberg (2004)

For Vision Sciences (broadly including experimental psychology, cognitive neuroscience, psychophysics, and clinical vision) Sternberg's apothegm is particularly poignant because stimuli are often presented in duration-, contrast-, or size-reduced fashion to probe the limits of vision, perception, and cognition. The goal is often to discover meaningful relationships between physical stimulus characteristics and psychological/physiological responses. With the stimulus as the starting point, fine control and reporting of presentation parameters is crucial for determining these relationships and allowing replication and extensions. At the same time, it is a nontrivial task to ensure that the apparatus (in modern labs often commodity computers and monitors) produce the displays as specified spatially, temporally, and chromatically. Experimental control has always been a concern of, and, in fact, defines, scientific psychological research. Researchers have developed many strategies and clever devices for measurement and control across the brass instrument era, the cabinet tachistoscope era, and the era of computer controlled cathode ray tubes (CRTs). Now flat panel displays are replacing CRTs in the lab and, in fact, it is rare to see CRTs at all in mainstream computer vendor catalogues. For certain types of experimentation where empirical claims do not hinge upon specific display parameters, the benefits of the flat panel displays make them an ideal drop-in replacement for CRTs. For more technically demanding experiments, it is only in the last 10 years or so that some backlit flat panel devices have been characterised as suitable or, in certain cases, better than CRTs (e.g., Kihara, Kawahara, & Takeda, 2010; Lagroix, Yanko, & Spalek, 2012; Wang & Nikolic', 2011), though there are limitations (see, e.g., Badano, 2004; Elze, Taylor, & Bex, 2013). With flat panel displays now a mainstream replacement for the laboratory CRT (e.g., Elze et al., 2013; Kihara et al., 2010; Wang & Nikolic', 2011) there are potential practical pitfalls paralleling those presented in the earlier technology transitions plus some new problems. The spatiotemporal creation of a visual stimulus on a CRT happens in a manner quite different from that on flat panel and these differences have implications for tachistoscopic experiments.

Overview and Plan

The plan of the paper is to briefly trace the concerns associated with tachistoscopic presentation from the first-generation devices in the mid 19th century to the now fourth-generation of tachistoscope with flat-panel devices to show that in some ways, the basic issues have not changed. Illustrative examples from published experimental works are discussed to clarify the relevant issues and a select set of technical papers containing methods and examples of measurements of modern display types is provided. These technical resources were chosen with an audience of vision science and cognition/perception researchers in mind and provide entry points to issues that affect stimulus presentation. Some of these entry points are outside the range of journals that an experimentalist might typically access. This is intentional because as the display technologies change, knowledge and experience from many disciplines will be relevant. Finally, the application of clarifying methodological language to several recent papers is given to highlight the importance of understanding (new) display technology. In the Appendix, a simple economical example of the photocell-on-the-display method for characterising CRT screen refreshes is provided to encourage researchers to measure rather than assume display times. Equipment and procedures for more sensitive and thorough characterisation of display timings is available in several of the papers cited below.

Two related themes are woven into this treatment of old, new, and emergent displays. …

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