A clarification of self-terminating versus exhaustive variances in serial and parallel models

A recent study published in Perception & Psychophysics (Donnelly, Found, & Miller, 1999) employs response time (RT) variances (in the form of standard deviations) in addition to mean RTs. Variances can contribute greatly to model testing. However, there is a danger of perpetuating the kinds of logical and methodological errors that have long attended research employing mean RTs alone. This commentary clarifies the theoretical and methodological issues, points out some new results concerning variability in search processes, and indicates how to resolve the global and specific challenges associated with identifying psychological mechanisms.     

Using response time distributions to examine top-down influences on attentional capture

Three experiments examined contingent attentional capture, which is the finding that cuing effects are larger when cues are perceptually similar to a target than when they are dissimilar to the target. This study also analyzed response times (RTs) in terms of the underlying distributions for valid cues and invalid cues. Specifically, an ex-Gaussian analysis and a vincentile analysis examined the influence of top-down attentional control settings on the shift and skew of RT distributions and how the shift and the skew contributed to the cuing effects in the mean RTs. The results showed that cue/target similarity influenced the size of cuing effects. The RT distribution analyses showed that the cuing effects reflected only a shifting effect, not a skewing effect, in the RT distribution between valid cues and invalid cues. That is, top-down attentional control moderated the cuing effects in the mean RTs through distribution shifting, not distribution skewing. The results support the contingent orienting hypothesis (Folk, Remington, & Johnston, Journal of Experimental Psychology: Human Perception and Performance, 18, 1030–1044, 1992) over the attentional disengagement account (Theeuwes, Atchley, & Kramer, 2000) as an explanation for when top-down attentional settings influence the selection of salient stimuli.     

The Adaptive Value of Lexical Connotation in Speech Perception

Previous work (e.g. Bargh, Chaiken, Govender, & Pratto, 1992; Fazio, Sanbonmatsu, Powell, & Kardes, 1986) has shown that objects are evaluated on a goodness/badness dimension automatically and preconsciously. Vakoch and Wurm (1997; Wurm & Vakoch, 1996) have found similar results using different stimuli and tasks. They found that auditory lexical decision times depend on dimensions of connotation (Evaluation, Potency, and Activity). Reaction times (RTs) from these studies were interpreted in terms of the evolutionary adaptiveness of different types of perceptual processing. The current study introduces a new way to define words, using two dimensions (Danger and Usefulness) rather than three, that allows a direct test of the adaptiveness model. RTs for nouns chosen for their adaptive significance were related to Usefulness and Danger, and to the interaction between Usefulness and Danger. A database of dimension weights is included.     

Making strides in modeling individual differences: reply to Leite, Ratcliff, and White (2007)

Leite, Ratcliff, and White (2007) claimed that the diffusion model (Ratcliff, 1978) could simulate the molar patterns in response times (RTs) from the multiple tasks observed by Chen, Hale, and Myerson (2007). We present our own simulations to clarify the underlying mechanisms and show that, as is predicted by the difference engine model (Myerson, Hale, Zheng, Jenkins, & Widaman, 2003), correlations across tasks are the key to the molar patterns in individual RTs. Although the diffusion model and other sequential-sampling models may be able to accommodate patterns of RTs across tasks like those studied by Chen et al., the difference engine is the only current model that actually predicts them.     

Auditory and audiovisual inhibition of return

Two experiments examined any inhibition-of-return (IOR) effects from auditory cues and from preceding auditory targets upon reaction times (RTs) for detecting subsequent auditory targets. Auditory RT was delayed if the preceding auditory cue was on the same side as the target, but was unaffected by the location of the auditorytarget from the preceding trial, suggesting that response inhibition for the cue may have produced its effects. By contrast, visual detection RT was inhibited by the ipsilateral presentation of a visual target on the preceding trial. In a third experiment, targets could be unpredictably auditory or visual, and no peripheral cues intervened. Both auditory and visual detection RTs were now delayed following an ipsilateral versus contralateral target in either modality on the preceding trial, even when eye position was monitored to ensure central fixation throughout. These data suggest that auditory target—target IOR arises only when target modality is unpredictable. They also provide the first unequivocal evidence for cross-modal IOR, since, unlike other recent studies (e.g., Reuter-Lorenz, Jha, & Rosenquist, 1996; Tassinari & Berlucchi, 1995; Tassinari & Campara, 1996), the present cross-modal effects cannot be explained in terms of response inhibition for the cue. The results are discussed in relation to neurophysiological studies and audiovisual links in saccade programming.     

Analysis of group differences in processing speed: Where are the models of processing?

Recently, Myerson, Adams, Hale, and Jenkins (2003) replied to arguments advanced by Ratcliff, Spieler, and McKoon (2000) about interpretations of Brinley functions. Myerson et al. (2003) focused on methodological and terminological issues, arguing that (1) Brinley functions are not quantile-quantile (QQ) plots of distributions of mean reaction times (RTs) across conditions; that the fact that the slope of a Brinley function is the ratio of the standard deviations of the two distributions of means has no implications for the use of slope as a measure of processing speed; that the ratio of slopes of RT functions for older and young subjects plotted against independent variables equals the Brinley function slope; and that speed-accuracy criterion effects do not account for slowing with age. We reply by showing that Brinley functions are plots of quantiles against quantiles; that the slope is best estimated by the ratio of standard deviations because there is variability in the distributions of mean RTs for both older and young subjects; that the interpretation of equality of the slopes Brinley functions and plots of RTs against independent variables in terms of processing speed is model dependent; and that speed-accuracy effects in some, but not all, experiments are solely responsible for Brinley slopes greater than 1. We conclude by reiterating the point that was not addressed in Myerson et al. (2003), that the goal of research should be modelbased accounts of processing that deal with correct and error RT distributions and accuracy.     

Test-Retest Reliability of the Emotional Stroop Task: Examining the Paradox of Measurement Change

The Emotional Stroop (ES) task (I. H. Gotlib & C. D. McCann, 1984) has been proposed as an experimental measure to assess the processing of emotion or the bias in attention of emotion-laden information. However, study results have not been consistent. To further examine its reliability for empirical research, the authors of this study administered the ES task to 33 participants on 2 separate occasions separated by 1 week. Results indicated that retest reliabilities for reaction times (RTs) derived from the 3 separate emotion conditions (manic, neutral, and depressive) across the 1 week interval were very high. However, consistent with previous research, the reliabilities were very low for the interference indices (manic and depressive). These low reliabilities reflect the very high intercorrelation between the RTs derived from the 3 conditions. The authors concluded that a better indicator of the reliability for this task is the individual RTs from each emotion condition.     

Differential Decline of Verbal and Visuospatial Processing Speed Across the Adult Life Span

The present study compared the age-related decline in verbal and visuospatial processing speed in 131 participants aged 18 to 90 years. Participants performed four verbal and four visuospatial tasks. Age differences in processing speed were compared at the group and individual levels. For the group-level analyses, participants were divided into a young adult group and six older groups subdivided by decade. The mean verbal and visuospatial response times (RTs) for each group were regressed on the corresponding RTs of the young adult group. The slope of the visuospatial regression was greater than that for the verbal regression at all ages, and the difference between the visuospatial and verbal slopes increased with each decade. For the individual-level analyses, a verbal and a visuospatial processing-time coefficient (Hale & Jansen, 1994) was obtained for each individual, and these values were then regressed on age. Verbal processing time increased linearly by approximately 50% while visuospatial processing time increased exponentially by approximately 500% from 18 to 90 years. Taken together, the results at both the group and the individual level demonstrate that aging affects visuospatial processing to a much greater extent than verbal processing.     

Tracking fear in snake and spider fearful participants during visual search: A multi-response domain study

In visual search tasks snake or spider fearful participants showed shorter reaction times (RTs) to respond to their feared animal (e.g., snake) than to the nonfeared animal (i.e., spider) (Öhman, Flykt, & Esteves, 2001). Here, we used this paradigm with heart rate (HR), RTs, and event-related potential (ERP) measures, to investigate the nature of the responses to the feared animal, a nonfeared (but fear-relevant) animal, and fear-irrelevant target stimuli with snake fearful, spider fearful, and nonfearful participants. Fearful participants showed shorter RTs and evoked larger amplitudes on a late positive potential (LPP; 500–700 ms) for their feared compared to the nonfeared and the fear-irrelevant targets. No relevant significant differences were found on early ERP components and HR measures. These findings do not support an involvement of early information processing in the detection of the feared animal in fearful participants, they favour instead a more elaborated analysis of these complex stimuli to achieve the detection.     

On the mean and variance of response times under the diffusion model with an application to parameter estimation

We give closed form expressions for the mean and variance of RTs for Ratcliff’s diffusion model [Ratcliff, R. (1978). A theory of memory retrieval. Psychological Review, 85, 59-108] under the simplifying assumption that there is no variability across trials in the parameters. These expressions are more general than those currently available. As an application, we demonstrate their use in a method-of-moments estimation procedure that addresses some of the weaknesses of the EZ method [Wagenmakers, E.-J., van der Maas, H. L. J., & Grasman, R. P. P. P. (2007). An EZ-diffusion model for response time and accuracy. Psychonomic Bulletin & Review, 14, 3-22], and illustrate this with lexical decision data. We discuss further possible applications.     

A model of rotated mirror/normal letter discriminations

Rotated mirror/normal letter discriminations are thought to require mental rotation in order to determine the direction of facing of the stimulus. The response time (RT) function over orientation tends to be curved, rather than the linear function found for other mental rotation tasks. The present study investigated the possibility that the curved RT function is a result of a mixture of trials requiring and not requiring mental rotation. The results suggested that the frequency of mental rotation is also a linear function of stimulus orientation. Moreover, the relationship between an individual's rate of plane rotation and the mean difference in RT between mirror and normal stimuli was replicated, supporting the suggestion that mirrored stimuli are flipped after they are spun (Hamm, Johnson, & Corballis, 2004). On the basis of the present findings, the entire RT function can be modeled by using only the mean RTs for upright and inverted stimuli.     

Responses on a lateralized lexical decision task relate to both reading times and comprehension

Research over the last few years has shown that the dominance of the left hemisphere in language processing is less complete than previously thought [Beeman, M. (1993). Semantic processing in the right hemisphere may contribute to drawing inferences from discourse. Brain and Language, 44, 80–120; Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36(9), 827–835; Weems, S. A., & Zaidel, E. (2004). The relationship between reading ability and lateralized lexical decision. Brain and Cognition, 55(3), 507–515]. Engaging the right brain in language processing is required for processing speaker/writer intention, particularly in those subtle interpretive processes that help in deciphering humor, irony, and emotional inference. In two experiments employing a divided field or lateralized lexical decision task (LLDT), accuracy and reaction times (RTs) were related to reading times and comprehension on sentence reading. Differences seen in RTs and error rates by visual fields were found to relate to performance. Smaller differences in performance between fields tended to be related to better performance on the LLDT in both experiments and, in Experiment 1, to reading measures. Readers who can exploit both hemispheres for language processing equally appear to be at an advantage in lexical access and possibly also in reading performance.     

The EZ diffusion method: Too EZ?

The diffusion model (Ratcliff, 1978) for fast two-choice decisions has been successful in a number of domains. Wagenmakers, van der Maas, and Grasman (2007) proposed a new method for fitting the model to data (“EZ”) that is simpler than the standard chisquare method (Ratcliff & Tuerlinckx, 2002). For an experimental condition, EZ can estimate parameter values for the main components of processing using only correct response times (RTs), their variance, and accuracy, not error RTs or the shapes of RT distributions. Wagenmakers et al. suggested that EZ produces accurate parameter estimates in cases in which the chi-square method would fail-specifically, experimental conditions with small numbers of observations or with accuracy near ceiling. In this article, I counter these claims and discuss EZ’s limitations. Unlike the chi-square method, EZ is extremely sensitive to outlier RTs and is usually less efficient in recovering parameter values, and it can lead to errors in interpretation when the data do not meet its assumptions, when the number of observations in an experimental condition is small, or when accuracy in an experimental condition is high. The conclusion is that EZ can be useful in the exploration of parameter spaces, but it should not be used for meaningful estimates of parameter values or for assessing whether or not a model fits data.     

On the causes and effects of inhibition of return

Unpredictive visual transient cues have a biphasic effect on reaction times (RTs) to peripheral onset targets. At relatively short (e.g., 150-msec) cue-target stimulus onset asynchronies (SOAs), RTs to targets at cued versus uncued locations are facilitated, whereas at relatively long SOAs (e.g., beyond 300 msec), they are inhibited. The present review explores the conditions under which this latter, inhibitory, effect-referred to as inhibition of return (IOR; Posner & Cohen, 1984)—is revealed and those conditions under which it is generated. We argue that the extant literature converges on the view that IOR reflects a motor response bias that is generated by the activation of an oculomotor program to fixate the cue. However, we reveal that current conceptualizations of IOR are based on a limited sampling of possible tests of the generation and measurement of IOR and indicate where further experimental research is critical.     

Comparing exemplar-retrieval and decision-bound models of speeded perceptual classification

The authors compared the exemplar-based random-walk (EBRW) model of Nosofsky and Palmeri (1997) and the decision-bound model (DBM) of Ashby and Maddox (1994; Maddox & Ashby, 1996) on their ability to predict performance in Garner’s (1974) speeded classification tasks. A key question was the extent to which the models could predict facilitation in the correlated task and interference in the filtering task, in situations involving integral-dimension stimuli. To obtain rigorous constraints for model evaluation, the goal was to fit the detailed structure of the response time (RT) distribution data associated with each individual stimulus in each task. Both models yielded reasonably good global quantitative fits to the RT distribution and accuracy data. However, the DBM failed to properly characterize the interference effects in the filtering task. Apparently, a fundamental limitation of the DBM is that it predicts that the fastest RTs in the filtering task should be faster than the fastest RTs in the control task, whereas the opposite pattern was observed in our data.     

Asymmetric dependencies in perceiving identity and emotion: Experiments with morphed faces

We investigated whether an asymmetric relationship between the perception of identity and emo-tional expressions in faces (Schweinberger & Soukup, 1998) may be related to differences in the rela-tive processing speed of identity and expression information. Stimulus faces were morphed across identity within a given emotional expression, or were morphed across emotion within a given identity. In Experiment 1, consistent classifications of these images were demonstrated across a wide range of morphing, with only a relatively narrow category boundary. At the same time, classification reaction times (RTs) reflected the increased perceptual difficulty of the morphed images. In Experiment 2, we investigated the effects of variations in the irrelevant dimension on judgments of faces with respect to a relevant dimension, using a Garner-type speeded classification task. RTs for expression classifica-tions were strongly influenced by irrelevant identity information. In contrast, RTs for identity classifi-cations were unaffected by irrelevant expression information, and this held even for stimuli in which identity was more difficult and slower to discriminate than expression. This suggests that differences in processing speed cannot account for the asymmetric relationship between identity and emotion per-ception. Theoretical accounts proposing independence of identity and emotion perception are dis-cussed in the light of these findings.     

Age, information processing speed, and intelligence

Two parallel, but independent, literatures have grown out of observations that individual differences in information processing speed, as expressed in performance on choice reaction time (C RT) tasks, modestly correlate with individual differences in age and IQ test performance. These associations have prompted theories that individual differences in information processing speed functionally determine individual differences in performance of all cognitive skills by people of different general intellectual ability (Eysenck, 1986; Jensen, 1985) or age (Salthouse, 1982, 1985).

The experiments on which this literature has been based suffer from methodological weaknesses, such that comparisons have only been made very early in practice and have only concerned mean latencies for correct responses. An experiment compared 90 volunteers aged from 50 through 79 years who were grouped in terms of their performance on the AH 4 (Heim, 1968) IQ test. It explored the joint and independent effects of individual differences in age and in IQ test score and the effects of practice on mean latencies (C RTs) on the shapes of distributions of correct and incorrect responses and on the limiting speeds with which accurate responses can be made (speed/error trade-off functions). We suggest that a plausible explanation for the results is that individual differences in age and in general ability influence C RTs mainly because they affect the efficiency with which responses can be controlled to maximize speed while maintaining accuracy.     

Responses on a lateralized lexical decision task relate to both reading times and comprehension

Research over the last few years has shown that the dominance of the left hemisphere in language processing is less complete than previously thought [Beeman, M. (1993). Semantic processing in the right hemisphere may contribute to drawing inferences from discourse. Brain and Language, 44, 80–120; Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36(9), 827–835; Weems, S. A., & Zaidel, E. (2004). The relationship between reading ability and lateralized lexical decision. Brain and Cognition, 55(3), 507–515]. Engaging the right brain in language processing is required for processing speaker/writer intention, particularly in those subtle interpretive processes that help in deciphering humor, irony, and emotional inference. In two experiments employing a divided field or lateralized lexical decision task (LLDT), accuracy and reaction times (RTs) were related to reading times and comprehension on sentence reading. Differences seen in RTs and error rates by visual fields were found to relate to performance. Smaller differences in performance between fields tended to be related to better performance on the LLDT in both experiments and, in Experiment 1, to reading measures. Readers who can exploit both hemispheres for language processing equally appear to be at an advantage in lexical access and possibly also in reading performance.     

Mental chronometry and individual differences: Modeling reliabilities and correlations of reaction time means and effect sizes

We used a general stage-based model of reaction time (RT) to investigate the psychometric properties of mean RTs and experimental effect sizes (i.e., differences in mean RTs). Using the model, formulas were derived for the reliabilities of mean RTs and RT difference scores, and these formulas provide guidance about the number of trials per participant needed to obtain reliable estimates of these measures. In addition, formulas were derived for various different types of correlations computed in RT research (e.g., correlations between a mean RT and an external non-RT measure, between two mean RTs, between a mean RT and an RT effect size). The analysis revealed that observed RT-based correlations depend on many parameters of the underlying processes contributing to RT. We conclude that these correlations often fail to support the inferences drawn from them and that their proper interpretation is far more complex than is generally acknowledged.