How do people order stimuli?

People may find it easier to construct an order after first representing stimuli on a scale or categorizing them, particularly when the number of stimuli to be ordered is large or when some of them must be remembered. Five experiments tested this hypothesis. In two of these experiments (1 and 3), we asked participants to rank line lengths or to rank photographs by artistic value. The participants provided evidence of how they performed these tasks, and this evidence indicated that they often made use of some preliminary representation—either a metric or a categorization. Two further experiments (2 and 4) indicated that people rarely produced rankings when given a choice of assessment measures for either the length of lines or the artistic value of photographs. In Experiment 5, when the number of lines was larger or lines were only visible one at a time, participants were faster at estimating line lengths as a percentage of the card covered than at rank ordering the lengths. Overall, the results indicate that ordering stimuli is not an easy or natural process when the number of stimuli is large or when the stimuli are not all perceptible at once. An implication is that the psychological measures available to individuals are not likely to be purely ordinal when many of the elements being measured must be recalled.     

Semantic processing of crowded stimuli?

Effects of semantic processing of crowded characters were investigated using numbers as stimuli. In an identification task, typical spacing effects in crowding were replicated. Using the same stimuli in a magnitude comparison task, a smaller effect of spacing was observed as well as an effect of response congruency. These effects were replicated in a second experiment with varying stimulus-onset asynchronies. In addition, decreasing performance with increasing onset-asynchrony (so-called type-B masking) for incongruent flankers indicates semantic processing of target and flankers. The data show that semantic processing takes place even in crowded stimuli. This argues strongly against common accounts of crowding in terms of early stimulus-driven impairments of processing.     

Arm-movement responses to Müller-Lyer stimuli

Similarities between eye- and arm-movement patterns during the Müller-Lyer illusion were investigated. The study was designed to find out if characteristics of a visual illusion would be reflected in tracings of an unseen ann. Six stimuli, three experimental and three control, were presented five times to each of seven Ss who were familiar with the illusion. Data were analyzed by measuring lengths of tracings and by making intraindividual comparisons using t tests for correlated means. Results for the arm were similar to those reported elsewhere for the eye. Arrows with outward-directed obliques were traced longer than arrows with inward-directed obliques, as well as longer than control stimuli. Agreement between eye- and arm-movement responses to the illusion lend support for using each technique to investigate stimuli that affect man’s distance metric.     

Do features of stimuli influence IAT effects?

The Implicit Association Test (Greenwald, McGhee, & Schwartz, 1998) is a categorization task intended to measure the strength of associations between concepts. The present research investigated the influence of individual stimuli on IAT effects. Exploring implicit attitudes of East and West Germans, we systematically manipulated relatedness of target stimuli to the attribute dimension and, simultaneously, relatedness of attribute stimuli to the target dimension. Two experiments demonstrate the influence of stimulus associations as one source that drives IAT effects. Depending on the strength and the direction of these cross-category associations, the result was either stronger IAT effects or a decline of IAT effects. Implications for theoretical models as well as for the interpretation of IAT effects are discussed.     

Freeze or flee? Negative stimuli elicit selective responding

Humans preferentially attend to negative stimuli. A consequence of this automatic vigilance for negative valence is that negative words elicit slower responses than neutral or positive words on a host of cognitive tasks. Some researchers have speculated that negative stimuli elicit a general suppression of motor activity, akin to the freezing response exhibited by animals under threat. Alternatively, we suggest that negative stimuli only elicit slowed responding on tasks for which stimulus valence is irrelevant for responding. To discriminate between these motor suppression and response-relevance hypotheses, we elicited both lexical decisions and valence judgments of negative words and positive words. Relative to positive words (e.g., kitten), negative words (e.g., spider) elicited slower lexical decisions but faster valence judgments. Results therefore indicate that negative stimuli do not cause a generalized motor suppression. Rather, negative stimuli elicit selective responding, with faster responses on tasks for which stimulus valence is response-relevant.     

Cost–benefit and distributional analyses of accessory stimuli

Accessory stimuli (AS) are task-irrelevant events (typically an auditory tone) that speed reaction time (RT). With two conditions (AS-present, AS-absent) it is unclear whether AS-presence causes benefits or AS-absence causes costs, possibly due to the expectancy violations. The current study added a third condition where AS were absent in blocks and not expected (pure blocks); in other blocks, AS occurred with a probability of 0.5 (mixed blocks), allowing cost-benefit analysis comparing AS-absent RTs in pure and mixed blocks. Results demonstrated RTs were slower when AS were absent, regardless of whether the absence occurred in a mixed block or a pure block, suggesting AS do provide a benefit to RT. Additionally, AS-facilitation across the RT distribution was analysed using cumulative distribution frequencies and ex-Gaussian parameter estimation. Both provided converging evidence that AS-facilitation increases towards the slower end of the RT distribution. The implications for the utility of AS paradigms are discussed.     

Can simultaneous speech stimuli be classified in parallel?

Reaction times to detect a known or unknown digit in paired or single auditory test stimuli were measured. The results suggest that in classification or matching tasks with stimuli belonging to separate verbal classes, parallel or selective processing may be possible. There was no interaction of type of task (classify vs match) with either dichotic vs mixed monaural presentation, or pairs vs single stimuli, or negative vs positive responses. An attempt was made to suggest the separate processing stages underlying performance in this task.     

Cortical integration of audio–visual speech and non-speech stimuli

Using fMRI we investigated the neural basis of audio–visual processing of speech and non-speech stimuli using physically similar auditory stimuli (speech and sinusoidal tones) and visual stimuli (animated circles and ellipses). Relative to uni-modal stimuli, the different multi-modal stimuli showed increased activation in largely non-overlapping areas. Ellipse-Speech, which most resembles naturalistic audio–visual speech, showed higher activation in the right inferior frontal gyrus, fusiform gyri, left posterior superior temporal sulcus, and lateral occipital cortex. Circle-Tone, an arbitrary audio–visual pairing with no speech association, activated middle temporal gyri and lateral occipital cortex. Circle-Speech showed activation in lateral occipital cortex, and Ellipse-Tone did not show increased activation relative to uni-modal stimuli. Further analysis revealed that middle temporal regions, although identified as multi-modal only in the Circle-Tone condition, were more strongly active to Ellipse-Speech or Circle-Speech, but regions that were identified as multi-modal for Ellipse-Speech were always strongest for Ellipse-Speech. Our results suggest that combinations of auditory and visual stimuli may together be processed by different cortical networks, depending on the extent to which multi-modal speech or non-speech percepts are evoked.     

Length illusions in conventional and single-wing Müller-Lyer stimuli

Warren and Bashford (1977) reported that eliminating one of the wing components from the conventional (i.e., two-wing) Müller-Lyer figures had no appreciable effect on the magnitude of the acute-angle (contraction) illusion but substantially reduced the magnitude of the obtuse-angle (expansion) illusion. In addition, they found that whereas the contractionary effects of the acute-angle components tended to be confined to the region of the shaft adjacent to the angles, the expansionary effects of the obtuse-angle components were more uniformly distributed across the shaft. Since these findings challenge many theories of the Müller-Lyer illusion, the purpose of the present investigation was to evaluate further Warren and Bashford's work with four experiments. Experiments 1 and 2 assessed length illusion magnitudes by requiring subjects to adjust either the length of a plain comparison line to match the length of the Müller-Lyer test figures (Experiment 1) or the length of comparison Müller-Lyer figures to match the length of plain test lines (Experiment 2). Experiments 3 and 4 used a bisection task to assess whether the illusory effects of the angle components are confined mainly to regions of the shaft adjacent to the angles. Consistent with most theories of the Müller-Lyer illusion, eliminating one of the wing components reduced both forms of the Müller-Lyer length illusion to a similar extent. In addition, the acute- and obtuse-angle forms yielded similar patterns of bisection errors, with substantial errors for regions of the shaft adjacent to the angles and negligible errors for regions of the shaft distant from the angles.     

Does negative priming imply preselective identification of irrelevant stimuli?

Responses to recently ignored stimuli are often slower than responses to new stimuli (negative priming). This slowing is thought to imply that the irrelevant stimuli were identified before the relevant stimuli were selected. The slowing may, however, reflect processing that occurred after the selection process had already begun. In two experiments, the opportunity for preselective identification of irrelevant stimuli was eliminated by presenting the irrelevant stimuli late within the trial. Negative priming failed to occur under these conditions.     

Tone‐affect compatibility with affective stimuli and affective responses

Three experiments examine multimodal integration of tone pitch (high/low), facial expression stimuli (happy/angry), and responses (happy/angry) in a compatibility paradigm. When the participants' task is to imitate facial expressions (Experiment 1), smiles are facilitated by high tones whereas frowns are facilitated by low tones. Experiments 2 and 3 further analyse this effect and show that there is both integration between the tone stimulus and the facial stimulus and between the tone stimulus and the facial response. Results suggest that pitch height is associated with emotion. An interpretation in terms of an embodied cognition approach that emphasizes an interweavement of perception and action is discussed.     

Can attention give a left-ear advantage for verbal stimuli?

Three independent groups of 8 subjects listened monaurally to a randomized list of 50 common and 50 rare words and responded ‘yes’ to rare words. Responses were analyzed for correct identifications of rare words. A 50:50 group heard an equal number of words in right and left ears and gave a small but non-significant right-ear superiority. A 66:34 group heard nearly twice as many words in the right ear as the left and gave a significant right-ear superiority. A 34:66 group heard nearly twice as many words in the left ear as the right and gave a significant left-ear superiority. Responses were also analyzed according to signal-detection theory. Implications are discussed for theories of ear advantages.     

Is there an advantage for recognizing multi-modal emotional stimuli?

Emotions can be recognized whether conveyed by facial expressions, linguistic cues (semantics), or prosody (voice tone). However, few studies have empirically documented the extent to which multi-modal emotion perception differs from uni-modal emotion perception. Here, we tested whether emotion recognition is more accurate for multi-modal stimuli by presenting stimuli with different combinations of facial, semantic, and prosodic cues. Participants judged the emotion conveyed by short utterances in six channel conditions. Results indicated that emotion recognition is significantly better in response to multi-modal versus uni-modal stimuli. When stimuli contained only one emotional channel, recognition tended to be higher in the visual modality (i.e., facial expressions, semantic information conveyed by text) than in the auditory modality (prosody), although this pattern was not uniform across emotion categories. The advantage for multi-modal recognition may reflect the automatic integration of congruent emotional information across channels which enhances the accessibility of emotion-related knowledge in memory.     

Category effects on estimates of stimuli: perception or reconstruction?

The present study examined a common category effect that has been reported in the literature: the tendency for estimates of individual stimuli to be biased toward the central value of the presented set of stimuli. Both encoding and reconstruction accounts of this central-tendency effect are considered. Plain vertical lines and vertical lines embedded in the Müller-Lyer illusion were estimated while still in view or from memory. Although bias due to the Müller-Lyer illusion remained constant across the two conditions, bias due to the context set (category) occurred only when stimuli were estimated from memory. The results suggest that the category bias occurs at a later stage of processing that the Müller-Lyer effect and offer support for a reconstruction account of category effects on stimulus estimation.     

Hick’s law equivalent for reaction time to individual stimuli

Hick’s law, one of the few law-like relationships involving human performance, expresses choice reaction time as a linear function of the mutual information between the stimulus and response events. However, since this law was first proposed in 1952, its validity has been challenged by the fact that it only holds for the overall reaction time (RT) across all the stimuli, and does not hold for the reaction time (RT_i) for each individual stimulus. This paper introduces a new formulation in which RT_i is a linear function of (1) the mutual information between the event that stimulus i occurs and the set of all potential response events and (2) the overall mutual information for all stimuli and responses. Then Hick’s law for RT follows as the weighted mean of each side of the RT_i equation using the stimulus probabilities as the weights. The new RT_i equation incorporates the important speed–accuracy trade-off characteristic. When the performance is error-free, RT_i becomes a linear function of two entropies as measures of stimulus uncertainty or unexpectancy. Reanalysis of empirical data from a variety of sources provide support for the new law-like relationship.     

When do irrelevant visual stimuli impair processing of identical targets?

Three experiments investigated whether the repeated-letter inferiority effect (RLIE) and repetition blindness (RB) are identical phenomena or not and how the RLIE can be reconciled with the flanker compatibility effect (FCE). Participants reported a masked target and ignored an unmasked distractor. We manipulated the type of distractor (identical, alternative target, or neutral), the order of presenting distractor and target, and the predictability of target location. When distractors preceded the targets, distractors identical to the target always caused deficits in target processing (i.e., RB). With simultaneous presentation, identical distractors caused deficits (i.e., an RLIE) for unpredictable target locations only. Yet the RLIE was significantly smaller than RB. This result suggests that simultaneously presented stimuli are identified serially, in random order, if target position is unpredictable. As a result, RB arises only in the 50% of all trials with identical distractors in which the distractor is identified before the target. With simultaneous presentation and predictable target location, however, parallel processing of targets and distractors was possible that gave rise to an FCE in recognition accuracy. Analyses of false alarm rates revealed no evidence of significant response biases.     

Structure in the classification of stimuli differing on several continuous attrjbutes’

Subjects were requested to sort sets of multidimensional stimuli differing in tint or shade, size, shape, and orientation. Each S received either 64 triangles selected at random from a larger population or 16 selected at random from the sample of 64. On one sort he was allowed to select the number ofcategories to be used; otherwise, he was required to distribute the stimuli among four, five, and six categories, respectively. The predominant strategy proved to be simple abstraction, with incomplete generalization a frequent alternative. On all but a few of the sorts, the sorting principle involved the use of one or a pair of attributes. In addition, Ss displayed a marked tendency toward numerical balance in their sorts and, when allowed to select the number of categories to be used, to limit them to a relatively small number. Imai has previously reported numerical balance and the use of a limited number of categories also to characterize the sorting of stimuli differing on discontinuous attributes. Informational measures proved helpful in describing such aspects of classification behavior as response uncertainty, numerical balance, and efficiency in abstraction.     

Are conditioned stimuli determinants of oriented exploratory behavior in the rat?

To test Bindra and Palfai's hypothesis about enhancing and inhibitory motivational effects of a conditioned stimulus on exploratory behavior, rats in a first experiment were submitted to pairings of a tone with (a) water, (b) intermittent deliveries of water after a period of constant pairing. In a control condition, the tone was presented alone. The tone was subsequently presented during oriented exploration of a novel stimulus, in the conditioning context. There was no difference in exploratory performance between conditions. In a second experiment with another kind of stimulus change and a larger number of training trials, exploration did not increase when occurring during CS presentation. The lack of facilitation which is possibly the product of competition between exploration and magazine-directed responses, can also be interpreted as indicating that the effects of a conditioned stimulus are reinforcer specific and that the diffuse activity it generates in a situation different from the training one is not equivalent, as concerns the processes involved, to oriented exploratory behavior.     

A procedure for obtaining young children’s reports of olfactory stimuli

Young children (ages 2 to 5) have proved to be difficult subjects for obtaining valid reports of their ratings of olfactory stimuli. Thirty-six preschoolers were tested on benzaldehyde (a pleasant odor) and on dimethyl disulfide (an unpleasant odor) using a smiling or frowning face as a response format. The results showed the ability of young children to discriminate between pleasant and unpleasant odors.