Selecting relevant signals from competing sensory inputs is a fundamental perceptual function. Although touch is good at detecting differences in vibration frequency, it struggles to select one stimulus element (signal) from another (distractor) based on a contingent difference in vibration frequency, at least when the signal and distractor are presented on the same fingertip. We investigated whether this limitation in feature-based selection persists even when the target and distractor streams were separated across the two hands. Participants judged the direction of apparent motion of a 40 Hz target while ignoring a 200 Hz distractor on the opposite hand. Across within-hand, between-hand, and diagonal motion paths, we compared single-stream baselines with conditions in which target and distractor motions were presented alternately or simultaneously. Direction judgments were accurate for single streams, but were impaired when participants selected the target by frequency. This impairment occurred even in the absence of temporal overlap and was further increased during simultaneous presentation. Therefore, in terms of limitations on signal selection based on features, contralateral separation alone was not enough to overcome the cost of feature integration of the tactile system.
The sense of number is a fundamental ability supported by dedicated neural mechanisms. Because natural scenes often contain multiple object groups, numerosity may be encoded in a category-specific manner. Consistent with this idea, adaptation effects are reduced when adaptor and test stimuli differ in category, particularly when category signals object identity (e.g., color but not motion). We asked whether this category-selectivity extends to other stimulus-history effects. Integrating past information into current perception may support the formation of discrete object representations from continuous input. Accordingly, both session-level (central tendency) and trial-level (serial dependence) biases may be category-tuned. We tested this hypothesis by manipulating color and motion features, each defining categories mapped to distinct numerosity ranges, presented either in blocked or interleaved sessions. Overall, we observed a comparable pattern across color and motion. At the session level, blocked presentations revealed a perceptual effect opposite to the compression predicted by range-specific central tendency. Interleaving abolished this effect and promoted convergence toward a prior shared across categories. At the trial level, the interleaved presentation provided both category repetitions and alternations, allowing us to examine how history effects unfold as a function of temporal lag and category match. We observed a characteristic temporal profile, with short-lag attraction, intermediate neutrality, and long-lag repulsion. Notably, attraction was category-independent, whereas repulsion was selectively observed for category repetitions. Overall, these findings show that multiple stimulus-history effects shape numerosity perception depending on the temporal and categorical structure of the environment, with category-selectivity primarily emerging in the repulsive bias.
Modal and amodal completions are considered distinct categories in the literature. Here, illusory figures are presented that possess modal qualities in some regions but appear amodal in others, despite appearing completely unoccluded. Data from 14 participants are suggestive of a seamless transition, which may be interpreted as weighing against the prevailing dichotomous view of modal and amodal percepts. This and alternative interpretations are discussed.
Leitmotivs, auditory characters, and sonic logos provide real-world examples of mid-level auditory stimuli. As a result of repeated exposure, they may come to be associated with, and hence to prime, a range of characters, objects, themes, products, or brands. As such, these mid-level auditory-conceptual associations provide intriguing examples of real-world crossmodal ‘meaning making’. Constraints on the acquisition of such associations have yet to be studied by cognitive neuroscientists. That said, an emerging body of research on the acquisition of crossmodal correspondences between simple sensory stimuli (such as colour patches and musical notes) suggests that the non-arbitrary choice of sound qualities for such mid-level auditory stimuli will likely mean that such sensory-conceptual associations are easier to learn than might otherwise be the case. We highlight a number of outstanding questions concerning the kinds of sensory correspondences and conceptual associations that hearing such mid-level auditory stimuli may elicit.
There has long been both scientific and artistic interest in the crossing of the senses of sight and sound, as evidenced by the “colour music” movement that swept through the arts just after the turn of the 19th century. Intriguingly, while many commentators (famously including Sir Isaac Newton) have attempted to align musical intervals with hue categories, there have also been others who, over the centuries, have suggested specific timbre–colour matchings, such as the suggestion that the colour scarlet is like the sound of the trumpet. The very ubiquity of this particular crossmodal correspondence between two simple sensory stimuli (involving hue and timbre, rather than, say, pitch) invites some kind of psychological explanation. Why exactly do these two stimuli appear so often in the literature, and why have they been so often mapped onto one another? In this opinion piece, we draw attention to this specific crossmodal correspondence, ask what it might mean to say that “the timbre of the trumpet is scarlet,” and assess various explanations that might help to explain its phenomenal salience to writers over the centuries. We end by considering the importance of determining the most intuitive crossmodal mappings for those wanting to design intuitive digital sensory substitution systems as well as effective sensory marketing solutions.
