The goal of avoiding distraction (e.g., ignoring words when naming their print colors in a Stroop task) is opposed intrinsically by the penchant to process conspicuous and correlated characteristics of the environment (e.g., noticing trial-to-trial associations between the colors and the words). To reconcile these opposing forces, the authors propose a tectonic theory of selective attention in which 2 memory-based structures--dimensional imbalance and dimensional uncertainty--drive selection by processing salient, surprising, and/or correlated information contained within and across stimulus dimensions. Each structure modulates the buildup of excitation to targets and the buildup of inhibition to distractors and to memories of previous stimuli. Tectonic theory is implemented to simulate the impact of 4 types of context on the presence, magnitude, and direction of congruity effects and task effects in the Stroop paradigm. The tectonic model is shown to surpass other formal models in explaining the range and diversity of Sroop effects.

The framework of dimensional interaction was used to test the hypothesis that the Stroop effect is partially rooted in mismatches in baseline discriminability, with stimulus differences along the word dimension typically exceeding stimulus differences along the color dimension. Subjects made speeded classifications, with either keypresses or vocalizations, of either words or colors. Stroop congruity and Garner interference were measured under conditions in which discriminabilities were (l) matched (Experiments 1 and 4), (2) mismatched in favor of colors (Experiment 2), or (3) mismatched in favor of words (Experiment 3). When matched, colors and words appeared separable, with small interactive effects being reduced or eliminated through practice. When mismatched, asymmetric Stroop and Garner effects emerged, with the more discriminable dimension disrupting classification of the less discriminable dimension. Asymmetric effects were obtained in both response modes, and were not alleviated by practice. We conclude that (1) the Stroop effect is an optional effect, and (2) unequal discriminability causes a mandatory failure of selective attention.In his comprehensive review, MacLeod (1991) noted that, since the seminal paper by Stroop in 1935, over 700 articles have explored some aspect of the phenomenon that Stroop discovered. Stroop's study is especially intriguing because of the peculiar asymmetry that characterized his subjects' performance: When they read color words printed in various colors, irrelevant color had no effect on performance; however, when they named the colors of these words, the irrelevant words hindered performance significantly. This asymmetry is known universally as the Stroop effect. Much is now known about how this effect relates to a host of experimental variables. Some ofthese relations are discussed below. Despite an enormous amount of empirical study, however, the wider theoretical implications of Stroop's work have largely eluded researchers. In the present study, we view the Stroop effect in a different light-namely, that of research and theory on dimensional interaction. This approach permits us to fit the Stroop effect comfortably into the broader framework of what factors cause selective attention to succeed or fail. Our efforts yield new insights into the nature of the Stroop effect, on the one hand, and the nature of selective attention, on the other. Selective Attention and Dimensional InteractionThe questions of whether and how humans integrate the separate sources of information in their environment have enjoyed considerable research focus within cognitive psychology. One reason is that these issues have great bearing on the nature of many fundamental cognitive processes, including those in perception (see, e.g., Ashby

This article presents findings of cross-sensory dimensional interaction for the visual dimension of vertical position and the auditory dimension of pitch. Subjects were simultaneously presented with attributes from both dimensions and performed speeded classification of one dimension. There were four task conditions. The irrelevant dimension was varied orthogonally or held constant, and attributes were always Synesthetically congruent or always Synesthetically incongruent. Subjects displayed reaction time (RT) interference when the second dimension varied orthogonally (a failure of selective attention). In addition, redundancy gain was asymmetric. Reaction time facilitation was only present when attributes were Synesthetically congruent. Negatively correlated redundancy (incongruence) yielded neither facilitation nor interference. Interaction was unaffected by changes in the spatial origin of signals (Experiment 3) and was still evident when signals were temporally separated (Experiment 4). Several explanations for these results are considered. It is argued that these results may represent a new form of dimensional interaction.Numerous introspective reports examining the intrinsic correspondences between various qualities of sense have shown substantial agreement among subjects. High-pitched tones are consistently judged as corresponding with bright hues (Simpson, Quinn, & Ausubel, 1956; Wicker, 1968). Light gray is judged to correspond with loud tones, whereas dark gray corresponds with soft tones (Bond & Stevens, 1965;Stevens & Marks, 1965). Such correspondences are called synesthetic (literally, joining of the senses) meaning that they reflect a presumed connection among attributes from different sensory modalities. These cross-modal matches are often speculated to be the product of some abstract, higher order cognitive process greatly removed from perception (Marks, 1975(Marks, , 1978 see Ortmann, 1933).However, the correspondences of the so-called synesthetes certainly appear not to be allegorical and inferential. Synesthetes are individuals who, when presented with a physical stimulus in one sense modality (e.g., a tone), report the actual experience of sensory stimulation in a separate modality (e.g., a sensation [called a photism] of a patch of color). The photisms of most synesthetes are quite vivid and compelling for the subject (e.g., Luria, 1968). Moreover, scrutiny of early case-study accounts (e.g., Ortmann, 1933; Werner, 1940;Wheeler and Cutsforth, 1922) suggests that for the synesthetes, the intrusion of internal, phenomenal sense information upon external, attended sense information creates an experience very close to the perceptual experience.' Interestingly, the correspondences commonly observed in their photisms are the same correspon-We wish to thank Bill Prinzmetal, James Pomerantz, and an anonymous reviewer for their very helpful comments on an earlier version of this article. We acknowledge the capable assistance of Paul Little, David Chandross, and Angelique Cooper in running the experi...

In two experiments, we examined whether or not pairs of auditory dimensions-timbre-loudness (Experiment 1) and timbre-pitch (Experiment 2)-interact in speeded classification. Subjects classified values from one dimension while the other dimension was (1) held constant (baseline), (2) varied orthogonally (filtering), or (3) correlated linearly. The subjects showed substantial Garner interference when classifying all dimensions-that is, poor performance at filtering relative to baseline. Timbre and loudness displayed redundancy gain (i.e., performance faster than baseline) when correlated positively, but redundancy loss (i.e., interference) when correlated negatively. Timbre and pitch displayed redundancy gain however dimensions were correlated. Both pairs of dimensions showed substantial effects of congruity: Attributes from one dimension were classified faster when paired with "congruent" attributes from the other dimension. The results are interpreted in terms of an interactive multichannel model of auditory processing.