Herbert Heuer

The present study investigated the impact of handedness on haptic and visual size comparisons. Moreover, we sought to determine whether strength differences between the hands are correlated with lateral differences between judged sizes. Therefore, 80 left-handed and 80 right-handed young adults (without additional constraints on individual characteristics except for those required by the experimental tasks) completed a bimanual haptic size-comparison task, a visual size-comparison task, and strength measurements of fingers, hands, and arms. In the haptic size-comparison task, we observed an impact of handedness: Both left- and right-handers underestimated the size of an object in their dominant hand relative to an object in their non-dominant hand. This hand-related bias was confined to the haptic modality; in the visual size-comparison task, we observed a small overestimation of stimulus size in the right visual hemifield, as compared to the left visual hemifield, in right-handers, but not in left-handers. The strength measurements revealed the expected superiority of the dominant effector over the non-dominant effector, but the strength asymmetries were not correlated with the bias in haptic size-comparisons. The observed impact of handedness on haptic size judgments represents a case of embodied perception in the haptic modality.

We investigate whether and how humans exploit the predictability of their environment by extracting statistical regularities about stimulus color or shape at different stimulus locations. In Experiment 1, participants discriminated between colors presented at two locations with one color being more frequent than another color at one location, and reversed relative frequencies at another location. In Experiment 2, participants made same-different judgements with regard to two stimuli presented serially at different locations. While the first stimulus (S1) occurred at fixation, the second stimulus (S2) occurred at one of two locations. One possible S2 occurred more frequently than the alternative S2 at one location, while relative frequencies were reversed at the other location. In both experiments, we observed faster responses to the locally more frequent stimulus than to the locally less frequent stimulus. Since the frequent and the infrequent stimulus required both responses equally often in Experiment 2, we conclude that the relative frequency effects originated at a perceptual level of processing. Three mechanisms for producing the location-specific effects of relative stimulus frequency are contrasted: short-term sequential effects, location-based expectations, and use-dependent facilitation. Based on additional statistical analyses of our results, we discarded sequential effects as an explanation. Deciding between expectations and facilitation is more difficult, but error patterns favor an account of our results in terms of use-dependent facilitation of the processing of a locally more frequent relative to a less frequent stimulus.

Humans adjust to the frequency of conflicting stimuli so that the detrimental behavioral effects of frequent conflicts become smaller than those of rare conflicts. These adjustments become contingent on the locations where frequent and infrequent conflicts have been encountered. Experimentally such phenomena are studied by means of conflict tasks, a prominent one being the Simon task of the present experiments. Our Simon task involved four stimulus locations (upper-left, upper-right, lower-left, lower-right). Conflict frequency was manipulated for two diagonally opposite locations. For example, conflict frequency was low at the upper-left location and high at the lower-right location. At the remaining (non-manipulated) locations conflict frequency was intermediate. In Experiment 1 participants responded to stimulus colors by pressing a left or right key, in Experiment 2 by pressing a lower or upper key. We observed larger conflict effects for the low-conflict location than for the high-conflict location. Crucially, these adjustments to conflict frequency transferred to non-manipulated locations depending on the response configuration: transfer regions were the left or right hemifield with left-right responses, but the lower or upper hemifield with lower-upper responses. Assuming that transfer regions around manipulated stimulus locations are defined by identical (or similar) spatial codes, the pattern of transfer suggests a process of weighted two-dimensional location coding. According to this notion, the spatial dimension that is relevant for response discrimination has stronger weight in the coding of stimulus locations than a response-irrelevant dimension, and can therefore produce anisotropic transfer of conflict-frequency effects around manipulated locations.

In choice between frequent and infrequent responses the Simon effect is larger for the frequent than for the infrequent response. We arbitrate between three hypotheses to account for this finding. The first hypothesis holds that it is a straightforward consequence of biased response preparation. The second hypothesis posits a facilitation of the shift of visual attention to the side of the prepared response in addition, and the third one an effect of the different frequencies of congruent and incongruent trials associated with the task-irrelevant stimulus locations. In three experiments we show the modulation of the Simon effect by relative response frequency, its independence from the distance between hands and monitor, and its almost complete elimination by valid response cues. These findings are in line with a primary role of biased response preparation. Consistent with this conclusion, in a model-based analysis, using extensions of the Leaky, Competing Accumulator model, differences between the probabilities of preparing the frequent and infrequent response were sufficient to produce the modulation of the Simon effect, though only poorly its dynamics as assessed by delta plots. However, these dynamics were produced by a model which implemented the hypothesis that response preparation implicates shielding against distraction in addition to anticipatory response activation. According to simulation results, the modulation of congruency effects by relative response frequency might depend on the particular type of congruency effect, specifically the temporal offset between the impacts of relevant and irrelevant stimuli.

Task such as hammering or throwing darts involve intentional actions performed with the anticipation of a desired effect that requires precision to achieve success. Visual perception of the goal, defined in an external frame of reference, plays a crucial role in specifying movement parameters in a body-centered frame of reference. Physical interruption of the task decouples the internal and external frames of reference leading to rapid performance decrements. Motor calibration, as noted by the ‘Calibration Effect’, is the fine-tuning of motor commands following performance-related feedback in the external frame of reference. Here we test the calibration effect with non-skilled populations in both a sport specific and an everyday type of task, darts and hammering. Participants performed 20 rounds of five attempts of hitting a goal with a stable bodily position. Between rounds they moved around to perturb the fine tuning. The first repetition within a round of repeated attempts was less accurate than the subsequent attempts within that same round, even if controlling for gradual learning effects. Thus, the calibration effect, a rapid component of warm-up, is present both in professional athletes and unskilled dart players as well as in everyday activities such as hammering.

Humans have to deal with conflicting information. This is studied in conflict tasks such as the Simon task or the flanker task. For example, participants respond with the left or right hand to the color of a stimulus (task-relevant stimulus feature) which is presented in a left or right position (irrelevant feature) in the Simon task or to a letter (relevant) which is flanked by same or different letters (irrelevant) in the flanker task. In incongruent trials, in which relevant and irrelevant stimulus features require different responses, reaction time is longer and errors are more frequent. This congruency effect is reduced after incongruent trials, dubbed congruency sequence effect (CSE). Here, we show that with temporally separated presentations of relevant and irrelevant stimulus features in the Simon task the CSE is strong with leading irrelevant feature, but declines with leading relevant feature. For the flanker task, this modulation of the CSE was unreliable. By means of an extended leaky, competing accumulator model, we contrasted two mechanisms of the CSE for the Simon task: gating of the irrelevant stimulus information and re-mapping of the stimulus positions to response positions after incongruent trials. The gating model failed to account for some aspects of the observed data which could be simulated by the re-mapping model. For the flanker task, there was not only a CSE, but also overall longer reaction times after incongruent trials. This required an extension of the re-mapping model in terms of higher response thresholds after incongruent than after congruent trials. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Previous studies revealed an S-R compatibility effect between physical stimulus size and response location, with faster left (right) responses to small (large) stimuli, respectively, as compared to the reverse assignments. Here, we investigated the locus of interactions between the processing of size and spatial locations. In Experiment 1, we explored whether stimulus size and stimulus location interact at a perceptual level of processing when responses lack spatiality. The stimuli varied on three feature dimensions (color, size, location), and participants responded vocally to each feature in a separate task. Most importantly, we failed to observe a size-location congruency effect in the color-naming task where S-R compatibility effects were excluded. In Experiment 2, responses to color were spatial, that is, key-presses with the left and right hand. With these responses there was a congruency effect. In addition, we tested the interaction of the size-location compatibility effect with the Simon effect, which is known to originate at the stage of response selection. We observed an interaction between the two effects only with a subsample of participants with slower reaction times (RTs) and a larger size-location compatibility effect in a control condition. Together, the results suggest that the size-location compatibility effect arises at the response selection stage. An extended leaky, competing accumulator model with independent staggered impacts of stimulus size and stimulus location on response selection fits the data of Experiment 2 and specifies how the size-location compatibility effect and the Simon effect can arise during response selection.

Our brain tends to combine multisensory signals based on their respective reliability. This reliability depends on sensory noise in the environment, noise in the nervous system, and, as we show here, variability induced by the specific judgment procedure.

Modifications of imagined sensory consequences will not benefit overt performance when they cannot be transformed into motor outflow that produces them. With physical practice, the acquisition of internal models of motor transformations is largely based on prediction errors that are absent in imagery practice. What can imagery practice nevertheless contribute to transformation learning? Explicit, strategic adjustments to novel transformations should be possible. This appears less likely for implicit adjustments. Are there variants of imagery practice that can produce adjustments without conscious awareness of the transformation and/or the resultant movement changes?