simulations Online of models for backward masking
Gregory Francis1 Purdue University Department of Psychological Sciences 703 Third Street West Lafayette, IN 47907-2004 11 July 2002 Revised: 30 January 2003 Final revision: 03 April 2003 Key words: masking, metacontrast, models, simulation, vision Running head: Online simulations for masking
1
E-mail: [e-mail]; phone: [phone]. This material is based upon work sup-
ported by the National Science Foundation under Grant No. 0108905.
Online simulations of masking Abstract
2
Five simulations of quantitative models of visual backward masking are available on the Internet at http://www.psych.purdue.edu/gfrancis/Publications/BackwardMasking/. The simulations can be run in a web browser that supports the Java programming language. This paper describes the motivation for making the simulations available and gives a brief introduction to how the simulations are used. The source code is available on the web page, and the paper describes how the code is organized.
Online simulations of masking
3
Introduction
Backward masking occurs when a briey presented visual target stimulus becomes dicult to see because of the appearance of a mask stimulus that follows the target. Backward masking has been investigated in thousands of studies with a variety of experimental manipulations g (see Breitmeyer & Omen (2000) and Enns & Di Lollo (2000) for recent reviews). There are three reasons that interest in the properties of masking has been strong for decades. First, vision scientists use masking to explore the interaction of the target and mask signals and identify key properties of the mechanisms involved in visual perception. Second, cognitive psychologists use backward masking as a means of interrupting the processing of target information. It is known that processing of a target does not stop with the physical disappearance of the target stimulus, but that processing can continue for at least a second after the stimulus has turned o (Sperling, 1960). The presentation of a strong mask seems to halt further processing of the target stimulus as soon as the mask appears. Thus, by varying the timing between the oset of the target and the onset of the mask, the duration of processing can be controlled and the details of cognitive mechanisms analyzed. Third, the properties of masking have been used to investigate aspects of various types of mental diseases (e.g., Bra & Saccuzzo, 1981; Green, Nuechterlein & Mintz, 1994; Slaghuis & Curran, 1999). Patients sometimes respond quite dierently than normals under masking conditions. Given the strong interest in masking and the frequency of its use as a tool for investigating perceptual, cognitive, and beha...
Francis2003b