The e-detection task 1 Running head : THE E-DETECTION TASK The e-detection task to measure the visibility of primes in masked-priming experiments

In masked priming studies the visibility of the primes depends on various factors besides the stimulus onset asynchrony between the prime and the target. Recent studies have indicated that researchers should be more careful about this aspect. We present an e-detection experiment that can easily be run in combination with the usual masked priming studies and that allows researchers to equate their presentation conditions and to assess the impact of various variables on the visibility of the primes. Two applications are given: One in which the prime visibilities in two different labs were compared, and one in which the implications of the insertion of a postmask between the prime and the target are examined. The e-detection task 3 The e-detection task to measure the visibility of primes in masked-priming experiments In recent years the masked priming procedure has become the task of choice for research on visual word recognition. In this procedure, a target word is preceded first by a forward mask consisting of non-letter symbols (e.g., #######) and then by a prime presented so briefly that it is either not visible or only barely visible. Participants have to make a decision about the target word or name it. Researchers are interested in the difference in response latencies as a function of the overlap between the prime and the target (the so-called priming effect). Different forms of overlap that have been studied are orthographic similarity (related trials nurse-CURSE vs. control trials towel-CURSE), phonological similarity (yuice-USE vs. douke-USE), morphological similarity (viewer-VIEW vs. ranger-VIEW), semantic relatedness (butter-BREAD vs. buster-BREAD), and translation equivalence (e.g., amour-LOVE vs. terre-LOVE). A variable that has received a lot of attention is the time delay between the onset of the prime and the onset of the target word, the so-called stimulus-onset-asynchrony (SOA). The briefer the exposure of the prime, the less perceptible it is and the less impact one expects from it. Typical exposure durations are 43 ms and 57 ms (these are multiples of the 14.3 ms refresh cycle of a typical 70 Hz computer monitor; Forster & Forster, 2003). Sometimes, researchers have used shorter SOAs (e.g., 14 or 29 ms) to examine whether orthographic, phonological, or semantic priming effects would still be observed at these exposure durations (see, e.g. Rastle and Brysbaert (2006) for a review of all the studies on the masked phonological priming effect in English). Tzur and Frost (2007) recently made the case that researchers interested in the impact of SOA have typically assumed that the presentation duration of the prime is the only variable that matters in masked priming with verbal stimuli. This assumption is grounded on the belief that the processing of the prime starts as soon as the prime is The e-detection task 4 presented and stops when the input of the prime is overwritten by the target. Throughout the years, there have been claims that this view is wrong as far as the end part is concerned. For instance, Dehaene et al. (1998) showed that the processing of the masked primes does not stop when the input is overwritten by the target stimulus, but continues all the way up to the motor cortex and results in response congruency effects. Tzur and Frost (2007) added to this that the processing of the stimulus not only depends on the time that is available between the onset of the prime and the onset of the target, but also on the total energy of the prime. Within the confines of a typical masked priming study, a prime with a higher contrast to the background will result in a stronger priming effect. So, researchers on visual word recognition have been misled by their conviction that the luminance of the stimuli and the background were of no importance. Tzur and Frost (2007) showed that depending on the luminance of the stimuli, a repetition priming effect could be present or absent at an SOA of 20 ms, leading them to advise researchers to report in their articles the luminance of the stimuli employed in the experimental setting, together with the screen contrast, the room luminance and the procedures used for dark adaptation. Unfortunately, measuring the physical properties of a display is a time-consuming process and would need to be repeated for each monitor more than once. For example, it may be that the screen properties vary depending on how long the monitor has been switched on. Further, there is the possibility of individual differences in sensitivity and dark adaptation, and there is even the possibility that the participants alter the contrast and brightness settings of the monitor themselves. Finally, even if we have physical measurements of the stimuli, they tell us relatively little about the visibility of the primes. Some non-linearity in the relationship between the luminance and the visibility of a stimulus is to be expected (Tzur & Frost, 2007), making it difficult to compare the obtained physical values in terms of their consequences for behavioural performance. A far The e-detection task 5 simpler and more direct way to measure the visibility of the prime is to administer a standardized detection task and to report the mean performance across all participants in the experiment on this task. Such a task is already in use for some time in the literature on unconscious processing. For instance, Greenwald, Klinger, and Schuh (1995) asked participants in some experiments to indicate on each trial whether a stimulus was presented or, in other experiments, where the stimulus was presented (left/right of the fixation location). Given that participants could not reliably perform this task under some conditions, it was concluded that these were conditions of unconscious processing if under those same conditions a masked priming effect was observed. A similar approach was suggested by Finkbeiner, Forster, Nicol, and Nakamura (2004). As part of their investigation of masked semantic and translation priming effects, they used an e-detection task in which participants were presented with the usual primes and targets, but this time they were not asked to make a decision about the target, but to indicate whether the prime contained the letter ”e” or not. The target was redundant in this task. By looking at the accuracy of the participants in the e-detection task, Finkbeiner et al. (2004) had objective information about the visibility of the primes in their study. Finkbeiner’s (2004) task is appealing because it is a very straightforward way to measure the visibility of primes. Participants are asked to make judgments about primes that are presented in exactly the same way as they were presented in the actual experiment. In addition, the task is short enough so that it can easily be run after the experimental session on the same participants who took part in the experiment, making it possible to take the characteristics of the participants into account. In the present series of experiments, we investigate whether an extended version of the e-detection task, including a wide variety of SOAs, could serve as a benchmark to calibrate the equipment and the experimental conditions before one engages in masked priming experiments. Including the results of the benchmarking procedure in papers would allow comparison of the results from different The e-detection task 6 laboratories with respect to the physical properties of their screens and the presentation parameters they used. The e-detection task we standardized includes English word and non-word primes followed by unrelated English target words. Participants have to indicate whether the prime contains the letter ”e” or not. Although we tested the task with English stimuli, there are good reasons to believe that the task also works for non-English speakers or speakers who have English as a second language, as we will see below.