Sabine Grimm

The human auditory system rapidly encodes auditory regularities. Evidence comes from the oddball paradigm, in which frequent (standard) sounds are occasionally replaced with a rare (deviant) sound. Deviants relative to standards typically elicit signs of prediction error (e.g., MMN and P3a). It is, however, less clear whether deviants, which also bear predictive information but are encountered less often than standards, might inform auditory prediction. To investigate this, naïve participants listened to sound sequences constructed according to a new, modified version of the oddball paradigm: two kinds of deviants differing in their probability of repetition yield the sound actually following a deviant either conditionally likely or unlikely. As this sound is either the same deviant (repetition) or a standard (no repetition), it is either unlikely or likely with respect to the global stimulus probability at the same time. In an active deviant detection task, we replicated previous behavioural findings, demonstrating that predictive information carried by deviants (conditional probability) is extracted when behaviourally relevant. Our analyses further reveal that respective response time effects increase over the course of the task. However, in a passive listening setting, both MMN and P3a were confined to violations of rules based on global probability, while not being sensitive to conditional probability. Though some sensitivity to conditional probability had been observed in a previous study, these effects were tiny compared to those of global probability. Thus, the auditory system seems to mainly rely on rules that are encountered frequently (standard regularity), at least during passive listening.

Gaze behavior during locomotion must balance the sampling of relevant information and the need for a stable gait. To maintain a safe gait in the light of declining resources, older adults might shift this balance toward the uptake of gait-related information. We investigated how violations of expectations affect gaze behavior and information uptake across age groups by asking younger and older adults to locomote through a virtual hallway, where they encountered expected and unexpected objects. We found that older adults look more on the floor, despite the translational locomotion, though not the rotational, being virtual. Dwell times on unexpected objects were increased in both age groups compared to expected objects. Although older adults showed shorter dwell times on expected objects, dwell times on unexpected objects were similar across age groups. Thus the difference between expected and unexpected objects was greater in older adults. Gaze distributions were more influenced by cognitive control capacities than by motor control capacities. Our findings indicate that unexpected information attracts attention during locomotion-particularly in older adults. However, during actual locomotion in the real world, increased information processing might come at the cost of reduced gait safety if processing resources are shifted away from stabilizing gait.

The human auditory system rapidly encodes auditory regularities. Evidence comes from the oddball paradigm, in which frequent (standard) sounds are occasionally replaced with a rare (deviant) sound. Deviants relative to standards typically elicit signs of prediction error (e.g., MMN and P3a). It is, however, less clear whether deviants, which also bear predictive information but are encountered less often than standards, might inform auditory prediction. To investigate this, naïve participants listened to sound sequences constructed according to a new, modified version of the oddball paradigm: two kinds of deviants differing in their probability of repetition, yield the sound actually following a deviant either conditionally likely or unlikely. As this sound is either the same deviant (repetition) or a standard (no repetition), it is either unlikely or likely with respect to the global stimulus probability at the same time. In an active deviant detection task, we replicated previous behavioural findings, demonstrating that predictive information carried by deviants (conditional probability) is extracted when behaviourally relevant. Our analyses further reveal that respective effects at the level of response times increase with time. However, in a passive listening setting both MMN and P3a were confined to violations of rules based on global probability, while not being sensitive to conditional probability. Though some sensitivity to conditional probability had been observed in a previous study, these effects were tiny compared to those of global probability. Thus, the auditory system seems to mainly rely on rules that are encountered frequently (standard regularity), at least during passive listening.

When viewing natural scenes, participants tend to direct their gaze towards the image center, the so-called "central bias." Unless the head is fixed, gaze shifts to peripheral targets are accomplished by a combination of eye and head movements, with substantial individual differences in the propensity to use the head. We address the relation of central bias and head-movement propensity. In one part of the experiment, participants viewed natural scenes of two different sizes without moving their head. We found that the central bias of each individual scaled with image size. In another experimental part, the same participants stood in the center of a panoramic screen and shifted their gaze to peripheral targets. Target eccentricities were either instructed by text (endogenous mode) or by a bar appearing at the target location (exogenous mode). In this "peripheral-target" task, we found a strong correlation between the exogenous and the endogenous mode, indicating that they provide a robust measure of an individual's head-movement propensity. Despite substantial inter-individual variability in both tasks, no significant correlation was found between head-movement propensity and central bias, and a trend toward significance for a specific measure was brittle. However, individuals with a higher head-movement propensity tended to have shorter fixation durations in scene viewing. Our results suggest that central bias in free scene viewing on typical screen sizes is predominately determined by visual properties. Although head-movement propensity seems to affect some aspects of scene-viewing behavior (fixation durations), individual differences in central bias are not explained by head-movement propensity.

Which properties of a natural scene affect visual search? We consider the alternative hypotheses that low-level statistics, higher-level statistics, semantics, or layout affect search difficulty in natural scenes. Across three experiments (n = 20 each), we used four different backgrounds that preserve distinct scene properties: (a) natural scenes (all experiments); (b) 1/f noise (pink noise, which preserves only low-level statistics and was used in Experiments 1 and 2); (c) textures that preserve low-level and higher-level statistics but not semantics or layout (Experiments 2 and 3); and (d) inverted (upside-down) scenes that preserve statistics and semantics but not layout (Experiment 2). We included “split scenes” that contained different backgrounds left and right of the midline (Experiment 1, natural/noise; Experiment 3, natural/texture). Participants searched for a Gabor patch that occurred at one of six locations (all experiments). Reaction times were faster for targets on noise and slower on inverted images, compared to natural scenes and textures. The N2pc component of the event-related potential, a marker of attentional selection, had a shorter latency and a higher amplitude for targets in noise than for all other backgrounds. The background contralateral to the target had an effect similar to that on the target side: noise led to faster reactions and shorter N2pc latencies than natural scenes, although we observed no difference in N2pc amplitude. There were no interactions between the target side and the non-target side. Together, this shows that—at least when searching simple targets without own semantic content—natural scenes are more effective distractors than noise and that this results from higher-order statistics rather than from semantics or layout.

It is often assumed that rendering an alert signal more salient yields faster responses to this alert. Yet, there might be a trade-off between attracting attention and distracting from task execution. Here we tested this in four behavioral experiments with eye-tracking using an abstract alert-signal paradigm. Participants performed a visual discrimination task (primary task) while occasional alert signals occurred in the visual periphery accompanied by a congruently lateralized tone. Participants had to respond to the alert before proceeding with the primary task. When visual salience (contrast) or auditory salience (tone intensity) of the alert were increased, participants directed their gaze to the alert more quickly. This confirms that more salient alerts attract attention more efficiently. Increasing auditory salience yielded quicker responses for the alert and primary tasks, apparently confirming faster responses altogether. However, increasing visual salience did not yield similar benefits: instead, it increased the time between fixating the alert and responding, as high-salience alerts interfered with alert-task execution. Such task interference by high-salience alert-signals counteracts their more efficient attentional guidance. The design of alert signals must be adapted to a “sweet spot” that optimizes this stimulus-dependent trade-off between maximally rapid attentional orienting and minimal task interference.

The auditory system has an amazing ability to rapidly encode auditory regularities. Evidence comes from the popular oddball paradigm, in which frequent (standard) sounds are occasionally exchanged for rare deviant sounds, which then elicit signs of prediction error based on their unexpectedness (e.g., MMN and P3a). Here, we examine the widely neglected characteristics of deviants being bearers of predictive information themselves; naive participants listened to sound sequences constructed according to a new, modified version of the oddball paradigm including two types of deviants that followed diametrically opposed rules: one deviant sound occurred mostly in pairs (repetition rule), the other deviant sound occurred mostly in isolation (non‐repetition rule). Due to this manipulation, the sound following a first deviant (either the same deviant or a standard) was either predictable or unpredictable based on its conditional probability associated with the preceding deviant sound. Our behavioral results from an active deviant detection task replicate previous findings that deviant repetition rules (based on conditional probability) can be extracted when behaviorally relevant. Our electrophysiological findings obtained in a passive listening setting indicate that conditional probability also translates into differential processing at the P3a level. However, MMN was confined to global deviants and was not sensitive to conditional probability. This suggests that higher‐level processing concerned with stimulus selection and/or evaluation (reflected in P3a) but not lower‐level sensory processing (reflected in MMN) considers rarely encountered rules.

There are sounds that most people perceive as highly unpleasant, for instance, the sound of rubbing pieces of polystyrene together. Previous research showed larger physiological and neural responses for such aversive compared to neutral sounds. Hitherto, it remains unclear whether habituation, i.e., diminished responses to repeated stimulus presentation, which is typically reported for neutral sounds, occurs to the same extent for aversive stimuli. We measured the mismatch negativity (MMN) in response to rare occurrences of aversive or neutral deviant sounds within an auditory oddball sequence in 24 healthy participants, while they performed a demanding visual distractor task. Deviants occurred as single events (i.e., between two standards) or as double deviants (i.e., repeating the identical deviant sound in two consecutive trials). All deviants elicited a clear MMN, and amplitudes were larger for aversive than for neutral deviants (irrespective of their position within a deviant pair). This supports the claim of preattentive emotion evaluation during early auditory processing. In contrast to our expectations, MMN amplitudes did not show habituation, but increased in response to deviant repetition—similarly for aversive and neutral deviants. A more fine‐grained analysis of individual MMN amplitudes in relation to individual arousal and valence ratings of each sound item revealed that stimulus‐specific MMN amplitudes were best predicted by the interaction of deviant position and perceived arousal, but not by valence. Deviants with perceived higher arousal elicited larger MMN amplitudes only at the first deviant position, indicating that the MMN reflects preattentive processing of the emotional content of sounds.

The auditory system has an amazing ability to rapidly encode auditory regularities. Evidence comes from the popular oddball paradigm, in which frequent (standard) sounds are occasionally exchanged for rare deviant sounds, which then elicit signs of prediction error based on their unexpectedness (e.g., MMN, P3a). Here, we examine the widely neglected characteristics of deviants being bearers of predictive information themselves: Naïve participants listened to sound sequence constructed according to a new, modified version of the oddball paradigm including two types of deviants that followed diametrically opposed rules: one deviant sound occurred mostly in pairs (repetition rule), the other deviant sound occurred mostly in isolation (non-repetition rule). Due to this manipulation, the sound following a first deviant (either the same deviant or a standard) was either predictable or unpredictable based on its conditional probability associated with the preceding deviant sound. Our behavioural results from an active deviant-detection task replicate previous findings that deviant repetition rules (based on conditional probability) can be extracted when behaviourally relevant. Our electrophysiological findings obtained in a passive-listening setting indicate that conditional probability also translates into differential processing at the P3a level. However, MMN was confined to global deviants and was not sensitive to conditional probability. This suggests that higher-level processing concerned with stimulus selection and/or evaluation (reflected in P3a) but not lower-level sensory processing (reflected in MMN) considers rarely encountered rules.