Modality effects in rhythm processing were examined using a tempo judgment paradigm, in which participants made speeding-up or slowing-down judgments for auditory and visual sequences. A key element of stimulus construction was that the expected pattern of tempo judgments for critical test stimuli depended on a beat-based encoding of the sequence. A model-based measure of degree of beat-based encoding computed from the pattern of tempo judgments revealed greater beat sensitivity for auditory rhythms than for visual rhythms. Visual rhythms with prior auditory exposure were more likely to show a pattern of tempo judgments similar to that for auditory rhythms than were visual rhythms without prior auditory exposure, but only for a beat period of 600 msec. Slowing down the rhythms eliminated the effect of prior auditory exposure on visual rhythm processing. Taken together, the findings in this study support the view that auditory rhythms demonstrate an advantage over visual rhythms in beat-based encoding and that the auditory encoding of visual rhythms can be facilitated with prior auditory exposure, but only within a limited temporal range. The broad conclusion from this research is that "hearing visual rhythms" is neither obligatory nor automatic, as was previously claimed by Guttman, Gilroy, and Blake (2005).

In music that is perceived as metrically structured, events coinciding with the main beat are called metrically accented. Are these accents purely cognitive, or do they perhaps represent illusory increases in perceived loudness or duration, caused by heightened attention to main beats? In four separate tasks, musicians tried to detect a small actual increase or decrease in the loudness or duration of a single note in melodies comprising 12 notes. Musical notation prescribed a meter (6/8) implying a main beat coinciding with every third note. Effects of metrical accentuation on detection performance were found in all four tasks. However, they reflected primarily an increase in sensitivity to physical changes in main beat positions, likely to be due to enhanced attention. There was no evidence of biases indicating illusory phenomenal accents in those positions. By contrast, and independent of metrical structure, pitch accents due to pitch contour pivots were often mistaken for increases in loudness.

The second of two consecutively presented sounds may be perceived as being longer than if that sound had been presented in isolation. We performed five experiments using heterophonic patterns in which a sine tone was preceded by a frequency-band noise. We observed significant overestimations of sine-tone duration, the size of which depended on intensity and frequency differences between the band noise and the sine tone (Experiments 1 and 2). Band noises that were considerably shorter than the sine tone still caused significant overestimations (Experiment 3). A short silent gap between the band noise and the sine tone strongly reduced the amount of overestimation (Experiment 4). Both frozen and nonfrozen band noises yielded overestimations (Experiment 5). Our explanation for the overestimation is that the onset of the sine tone is blurred by the band noise and that such a blurred onset is restored at the level of perceptual organization following rules of a simple auditory grammar. This restoration takes mental processing time, which adds to the perceived duration of the sine tone. We call this illusion time stretching and discuss the notion that subsequent temporal assimilation and/or contrast effects can dilate or compress the amount of stretching.

How constant is the Weber fraction (WF) for brief time intervals? This question was assessed in three experiments with two base durations (BDs), 0.2 and 1 sec, and with different ways of estimating the WF. In Experiment 1, the psychometric functions were drawn on the basis of 4, 8, or 12 comparison intervals with the shortest to longest duration ranges being kept constant. The results revealed no effect of the number of intervals, but the WF (threshold/BD) was significantly lower at 0.2 sec. In Experiment 2, the comparison intervals were distributed over three duration ranges. There was no range effect, and the WF was generally lower at 0.2 sec than at 1 sec. In Experiment 3, one condition allowed a comparison of the BD with the same range between the shortest and longest comparison intervals. Once again, the WF was lower at 0.2 sec than at 1 sec. Overall, the results reveal (1) that increasing the number of comparison intervals or the duration range does not seem to affect the value of the WF and (2) that the WF is lower at 0.2 sec than at 1 sec, which is inconsistent with the scalar property of some timing models.

Medical images constitute a core portion of the information a physician utilizes to render diagnostic and treatment decisions. At a fundamental level, this diagnostic process involves two basic processes: visually inspecting the image (visual perception) and rendering an interpretation (cognition). The likelihood of error in the interpretation of medical images is, unfortunately, not negligible. Errors do occur, and patients' lives are impacted, underscoring our need to understand how physicians interact with the information in an image during the interpretation process. With improved understanding, we can develop ways to further improve decision making and, thus, to improve patient care. The science of medical image perception is dedicated to understanding and improving the clinical interpretation process.

Speech perception (SP) most commonly refers to the perceptual mapping from the highly variable acoustic speech signal to a linguistic representation, whether it be phonemes, diphones, syllables, or words. This is an example of categorization, in that potentially discriminable speech sounds are assigned to functionally equivalent classes. In this tutorial, we present some of the main challenges to our understanding of the categorization of speech sounds and the conceptualization of SP that has resulted from these challenges. We focus here on issues and experiments that define open research questions relevant to phoneme categorization, arguing that SP is best understood as perceptual categorization, a position that places SP in direct contact with research from other areas of perception and cognition.

Rewards have long been known to modulate overt behavior. But their possible impact on attentional and perceptual processes is less well documented. Here, we study whether the (changeable) reward level associated with two different pop-out targets might affect visual search and trial-to-trial target repetition effects (see Maljkovic & Nakayama, 1994). Observers searched for a target diamond shape with a singleton color among distractor diamond shapes of another color (e.g., green among red or vice versa) and then judged whether the target had a notch at its top or bottom. Correct judgments led to reward, with symbolic feedback indicating this immediately; actual rewards accumulated for receipt at study end. One particular target color led to a higher (10:1) reward for 75% of its correct judgments, whereas the other singleton target color (counterbalanced over participants) yielded the higher reward on only 25% of the trials. We measured search performance in terms of inverse efficiency (response time/proportion correct). The reward schedules not only led to better performance overall for the more rewarding target color, but also increased trial-to-trial priming for successively repeated targets in that color. The actual level of reward received on the preceding trial affected this, as did (orthogonally) the likely level. When reward schedules were reversed within blocks, without explicit instruction, corresponding reversal of the impact on search performance emerged within around 6 trials, asymptoting at around 15 trials, apparently without the observers' explicit knowledge of the contingency. These results establish that pop-out search and target repetition effects can be influenced by target reward levels, with search performance and repetition effects dynamically tracking changes in reward contingency.

Although it has been argued that visual attention and the dynamics of binocular rivalry are closely linked, strong evidence for this proposition is still lacking. Here, we investigate how perceptual alternations during binocular rivalry are affected by spatial attention by employing a cuing paradigm. We show a tight link between the occurrence of perceptual alternations and the spatiotemporal properties of visual attention: Alternations occurred earlier and more frequently at locations where visual attention was summoned by an exogenous cue. We argue that cuing a location where rival images are presented leads to a transient increase in the effective contrast of these rival images. This transient increase in effective contrast increases the probability of an alternation at that location. Furthermore, we suggest that an occipito-fronto-parietal network known to be involved in selective attention and binocular rivalry mediates perceptual alternations by boosting the neural response at attended locations.