Michael E. J. Masson

Using confidence intervals in within-subject designs

We argue that to best comprehend many data sets, plotting judiciously selected sample statistics with associated confidence intervals can usefully supplement, or even replace, standard hypothesis-testing procedures. We note that most social science statistics textbooks limit discussion of confidence intervals to their use in between-subject designs. Our central purpose in this article is to describe how to compute an analogous confidence interval that can be used in within-subject designs. This confidence interval rests on the reasoning that because between-subject variance typically plays no role in statistical analyses of within-subject designs, it can legitimately be ignored; hence, an appropriate confidence interval can be based on the standard within-subject error term—that is, on the variability due to the subject × condition interaction. Computation of such a confidence interval is simple and is embodied in Equation 2 on p. 482 of this article. This confidence interval has two useful properties. First, it is based on the same error term as is the corresponding analysis of variance, and hence leads to comparable conclusions. Second, it is related by a known factor (√2) to a confidence interval of the difference between sample means; accordingly, it can be used to infer the faith one can put in some pattern of sample means as a reflection of the underlying pattern of population means. These two properties correspond to analogous properties of the more widely used between-subject confidence interval.

A tutorial on a practical Bayesian alternative to null-hypothesis significance testing

Null-hypothesis significance testing remains the standard inferential tool in cognitive science despite its serious disadvantages. Primary among these is the fact that the resulting probability value does not tell the researcher what he or she usually wants to know: How probable is a hypothesis, given the obtained data? Inspired by developments presented by Wagenmakers (Psychonomic Bulletin & Review, 14, 779–804, 2007), I provide a tutorial on a Bayesian model selection approach that requires only a simple transformation of sum-of-squares values generated by the standard analysis of variance. This approach generates a graded level of evidence regarding which model (e.g., effect absent [null hypothesis] vs. effect present [alternative hypothesis]) is more strongly supported by the data. This method also obviates admonitions never to speak of accepting the null hypothesis. An Excel worksheet for computing the Bayesian analysis is provided as supplemental material.

Evocation of functional and volumetric gestural knowledge by objects and words

We distinguish between grasping gestures associated with using an object for its intended purpose (functional) and those used to pick up an object (volumetric) and we develop a novel experimental framework to show that both kinds of knowledge are automatically evoked by objects and by words denoting those objects. Cued gestures were carried out in the context of depicted objects or visual words. On incongruent trials, the cued gesture was not compatible with gestures typically associated with the contextual item. On congruent trials, the gesture was compatible with the items functional or volumetric gesture. For both gesture types, response latency was longer for incongruent trials indicating that objects and words elicited both functional and volumetric manipulation knowledge. Additional evidence, however, clearly supports a distinction between these two kinds of gestural knowledge. Under certain task conditions, functional gestures can be evoked without the associated activation of volumetric gestures. We discuss the implication of these results for theories of action evoked by objects and words, and for interpretation of functional imaging results.

Reenacting the route to interpretation: Enhanced perceptual identification without prior perception

Memory for processing a stimulus event may be expressed indirectly through more fluent processing of that stimulus on a later occasion. In 11 experiments, enhanced identification of words presented under visual masking was measured following events that involved reading target words or generating them from semantic cues. Amount of enhancement was related not to whether a word was actually seen on its first presentation, but to the degree to which it was integrated with its encoding context—integration led to less enhancement. It is proposed that 2 sets of operations are carried out during encoding. Interpretive encoding operations construct a context-sensitive interpretation of the stimulus and are optionally followed by elaborative encoding operations. Enhanced word identification due to memory for a prior episode is determined by the fluent reenactment of interpretive encoding operations applied during that episode.

Beyond spreading activation: An influence of relatedness proportion on masked semantic priming

Semantic priming in the lexical decision task has been shown to increase when the proportion of related-prime trials is increased. This finding typically is taken as evidence for a conscious, strategic use of primes. Three experiments are reported in which masked semantic primes displayed for only 45 msec were tested in high- versus low-relatedness proportion conditions. Relatedness proportion was increased either by using a high proportion of semantically related primes or a large set of repetitionprimed filler trials. Semantic priming was consistently enhanced relative to a low-relatedness proportion condition. These relatedness proportion effects were not due to conscious, strategic use of primes: Exclusion of prime-aware subjects did not attenuate the effects, and better performance in a prime classification task was not associated with larger semantic priming effects. These results are interpreted within a retrospective account of semantic priming in which recruitment of a prime event is modulated by prime validity.

Grasping beer mugs: on the dynamics of alignment effects induced by handled objects.

We examined automatic spatial alignment effects evoked by handled objects. Using color as the relevant cue carried by an irrelevant handled object aligned or misaligned with the response hand, responses to color were faster when the handle aligned with the response hand. Alignment effects were observed only when the task was to make a reach and grasp response. No alignment effects occurred if the response involved a left-right key press. Alignment effects emerged over time, becoming more apparent either when the color cue was delayed or when relatively long, rather than short, response times were analyzed. These results are consistent with neurophysiological evidence indicating that the cued goal state has a modulatory influence on sensorimotor representations, and that handled objects initially generate competition between neural populations coding for a left- or right-handed action that must be resolved before a particular hand is favored.

Sources of bias in the Goodman-Kruskal gamma coefficient measure of association: implications for studies of metacognitive processes.

In many cognitive, metacognitive, and perceptual tasks, measurement of performance or prediction accuracy may be influenced by response bias. Signal detection theory provides a means of assessing discrimination accuracy independent of such bias, but its application crucially depends on distributional assumptions. The Goodman-Kruskal gamma coefficient, G, has been proposed as an alternative means of measuring accuracy that is free of distributional assumptions. This measure is widely used with tasks that assess metamemory or metacognition performance. The authors demonstrate that the empirically determined value of G systematically deviates from its actual value under realistic conditions. A distribution-specific variant of G, called G-sub(c), is introduced to show why this bias arises. The findings imply that caution is needed when using G as a measure of accuracy, and alternative measures are recommended.

Identification of typographically transformed words: Instance-based skill acquisition.

Two hypotheses concerning the development of skill at identifying typographically transformed words were tested. One claim is that a general skill independent of specific training instances is involved, and the other is that skill is based on memory for the analysis of specific instances encountered during training. Contrary to the general skill view, a series of experiments demonstrated that transfer of word identification skill was highly specific and occurred only when training and test instances shared common letters printed in the same case (i.e., uppercase or lowercase). Transfer of skill also depended on the visual patterns formed by adjacent letters and word shape. Presentation of a word in training and test phases significantly improved test phase identification of that word even when a unique visual pattern was used. These results are compatible with an instance-based view of word identification skill in which it is assumed that subjects develop skilled analysis of the visual and conceptual characteristics of specific words, and that this skill can be used to identify repeatedly presented words as well as predictable sets of novel words.

Conceptual processing of text during skimming and rapid sequential reading

Potential conceptual processing difficulties associated with abbreviating the duration of eye fixations during reading were explored using a rapid sequential visual presentation (RSVP) paradigm in which each word of a text was briefly presented (for as little as 86 msec) at a fixed location. Question answering and accuracy of summaries associated with RSVP were found to be inferior to performance obtained when subjects skimmed conventionally presented passages. RSVP performance was enhanced by inserting brief pauses between sentences. The pauses produced only minor changes in the perceptual characteristics of RSVP, but they probably allowed subjects to more readily process information that had been buffered in working memory. These results imply that eye fixation durations in conventional reading reflect the time constraints of conceptual processing operations (as well as constraints of planning and initiating eye movements), but also that these conceptual operations may be distributed over later fixations and even postponed until a syntactic boundary is reached.

Cognitive Control in Children Stroop Interference and Suppression of Word Reading

The development of cognitive control and its relation to overcoming Stroop interference was assessed in a sample (N = 65) of elementary-school children. Subjects alternately performed Stroop color-naming trials and word-reading trials. In separate blocks, the colored Stroop items were non-color words (incongruent condition) or rows of asterisks (neutral condition). Younger children showed both larger Stroop interference in error rates and a greater slowing of word reading in the incongruent condition compared with older children. We conducted analyses of response time distributions that assessed the degree of word-reading suppression applied by younger and older children. Surprisingly, these analyses indicated that younger children engaged in stronger suppression than older children. We propose that greater Stroop interference among younger children is not due to lack of ability to suppress word reading, but instead is the result of a failure to consistently maintain the task set of color naming.