Auditory attentional selection is biased by reward cues

On the temporal dynamics of reward utilization in dual-task situations

In dual-task (DT) situations, performance typically deteriorates compared with single-tasking situations. These decrements can be explained by the serial scheduling of response selection stages constituting a central bottleneck as with decreasing stimulus-onset asynchrony (SOA) the reaction time for the second task (Task 2; RT2) increases. Prior studies indicated that the reaction time for the first task (Task 1; RT1) and RT2 are improved in reward compared with no-reward conditions for a block-wise reward prospect, which reflects reward-related optimization in DT processing. However, it remains unclear whether participants can flexibly utilize reward information in a trial-by-trial manner to achieve reward-related improvements. Additionally, it is unclear whether a potential reward-related optimization reflects optimized task preparation only or whether the prospect of reward can evoke an additional task optimization mechanism that extends beyond preparation-related processing improvements. For Experiment 1, we combined a trial-wise reward prospect for participants' Task 1 performance, which was signaled by a cue before Task 1 onset, with block-wise presented cue-target intervals (CTI) of either 200 ms or 700 ms, resulting in precise temporal predictability of Task 1 onset by participants. First, we observed a reduced RT1 in the reward compared with the no-reward condition. Furthermore, the reward effects increased on RT2 for short compared with long SOAs, reflecting effect propagation at short SOA from Task 1 onto Task 2. Second, RTs decreased with increasing CTI, while reward effects increased with increasing CTI. Consequently, preparation-related processing improvements of DT performance were additionally improved by reward utilization. For Experiment 2, temporal predictability of Task 1 onset was reduced compared with Experiment 1 by presenting CTIs randomized within blocks, which allowed replicating the result pattern of Experiment 1. Across both experiments, the results indicate that participants can flexibly utilize reward information in a trial-by-trial manner and that reward utilization additionally improves preparation-related processing improvements for DT conditions with predictable and less predictable Task 1 onset.

On the localization of reward effects in overlapping dual tasks

In dual-task (DT) situations, performance deteriorates compared with single-task situations. Such performance decrements are frequently explained with the serial scheduling of the response selection stages constituting a bottleneck. Proof of this assumption stems from the observation that response times for the second task (task 2; RT 2) increase with decreasing stimulus-onset asynchrony (SOA).In this study, we investigated how the reward prospect for task 1 performance affects task 1 and task 2 processing. For that purpose, we relied on the psychological refractory period paradigm (PRP) as a chronometric tool, to determine the locus of the reward effect in the processing chain of both tasks.We obtained improved task 1 and task 2 performance; as indicated by reduced RTs in the reward compared to the no reward condition of task 1 and task 2. Furthermore, the reward effect propagated at short SOA from task 1 onto task 2, suggesting that the locus of the reward effect can be pinpointed before or at the bottleneck of task 1. Importantly, the mean reward effect on task 1 was increased compared to task 2, thus indicating that parts of the reward effect were not propagated onto task 2, therefore affecting task 1 motor processes.In Experiment 2, we tested for the locus of the effect propagation to task 2. Therefore, we implemented a difficulty manipulation of the response selection of task 2. The results indicate that the reward effect is propagated from task 1 onto the response selection stage of task 2.

Interaction of spatial attention and the associated reward value of audiovisual objects

Reward value and selective attention both enhance the representation of sensory stimuli at the earliest stages of processing. It is still debated whether and how reward-driven and attentional mechanisms interact to influence perception. Here we ask whether the interaction between reward value and selective attention depends on the sensory modality through which the reward information is conveyed. Human participants first learned the reward value of uni-modal visual and auditory stimuli during a conditioning phase. Subsequently, they performed a target detection task on bimodal stimuli containing a previously rewarded stimulus in one, both, or neither of the modalities. Additionally, participants were required to focus their attention on one side and only report targets on the attended side. Our results showed a strong modulation of visual and auditory event-related potentials (ERPs) by spatial attention. We found no main effect of reward value but importantly we found an interaction effect as the strength of attentional modulation of the ERPs was significantly affected by the reward value. When reward effects were examined separately with respect to each modality, auditory value-driven modulation of attention was found to dominate the ERP effects whereas visual reward value on its own led to no effect, likely due to its interference with the target processing. These results inspire a two-stage model where first the salience of a high reward stimulus is enhanced on a local priority map specific to each sensory modality, and at a second stage reward value and top-down attentional mechanisms are integrated across sensory modalities to affect perception.

The persistence of value-driven attention capture is task-dependent

Visual features previously associated with reward can capture attention even when task-irrelevant, a phenomenon known as value-driven attention capture (VDAC). VDAC persists without reinforcement, unlike other forms of learning, where removing reinforcement typically leads to extinction. In five experiments, factors common to many studies were manipulated to examine their impact on VDAC and its extinction. All experiments included learning and test phases. During learning, participants completed a visual search task during which one of two target colors was associated with a reward, and the other with no reward. During test, 1 week later, participants completed another visual search task in which the reward association was not reinforced. When a rewarded feature remained task-relevant (Experiment 1), VDAC was observed. When the rewarded feature was made task-irrelevant (Experiments 2-5) there was no evidence of a VDAC effect, except when the target feature was physically salient and there was a reduction in the frequency of exposure to the reward-associated feature (Experiment 5). We failed to find evidence of VDAC in Experiments 2-4, suggesting that VDAC may depend on the demands of the task resulting in vulnerability to VDAC. When VDAC was observed, extinction was also observed. This indicates that VDAC is subject to extinction as would be expected from an effect driven by reinforcement learning.

Value-driven modulation of visual perception by visual and auditory reward cues: The role of performance-contingent delivery of reward

Perception is modulated by reward value, an effect elicited not only by stimuli that are predictive of performance-contingent delivery of reward (PC) but also by stimuli that were previously rewarded (PR). PC and PR cues may engage different mechanisms relying on goal-driven versus stimulus-driven prioritization of high value stimuli, respectively. However, these two modes of reward modulation have not been systematically compared against each other. This study employed a behavioral paradigm where participants' visual orientation discrimination was tested in the presence of task-irrelevant visual or auditory reward cues. In the first phase (PC), correct performance led to a high or low monetary reward dependent on the identity of visual or auditory cues. In the subsequent phase (PR), visual or auditory cues were not followed by reward delivery anymore. We hypothesized that PC cues have a stronger modulatory effect on visual discrimination and pupil responses compared to PR cues. We found an overall larger task-evoked pupil dilation in PC compared to PR phase. Whereas PC and PR cues both increased the accuracy of visual discrimination, value-driven acceleration of reaction times (RTs) and pupillary responses only occurred for PC cues. The modulation of pupil size by high reward PC cues was strongly correlated with the modulation of a combined measure of speed and accuracy. These results indicate that although value-driven modulation of perception can occur even when reward delivery is halted, stronger goal-driven control elicited by PC reward cues additionally results in a more efficient balance between accuracy and speed of perceptual choices.

Cross-modal generalization of value-based attentional priority

This study aimed to determine whether value-based attentional biases learned in the auditory domain can correspondingly shape visual attention. A learning phase established associations between auditory words and monetary rewards via a modified version of the dichotic listening task. In a subsequent test phase, participants performed a Stroop task including written representations of auditory words previously paired with reward and semantic associates of formerly rewarded words. Results support a semantic generalization of value-driven attention from the auditory to the visual domain. The findings provide valuable insight into a critical aspect of adaptation and the understanding of maladaptive behaviors (e.g., addiction).

Adding noise is a confounded nuisance

A wide variety of research and clinical assessments involve presenting speech stimuli in the presence of some kind of noise. Here, I selectively review two theoretical perspectives and discuss ways in which these perspectives may help researchers understand the consequences for listeners of adding noise to a speech signal. I argue that adding noise changes more about the listening task than merely making the signal more difficult to perceive. To fully understand the effects of an added noise on speech perception, we must consider not just how much the noise affects task difficulty, but also how it affects all of the systems involved in understanding speech: increasing message uncertainty, modifying attentional demand, altering affective response, and changing motivation to perform the task.

Reward magnitude enhances early attentional processing of auditory stimuli

Reward associations are known to shape the brain's processing of visual stimuli, but relatively less is known about how reward associations impact the processing of auditory stimuli. We leveraged the high-temporal resolution of electroencephalography (EEG) and event-related potentials (ERPs) to investigate the influence of low- and high-magnitude stimulus-reward associations in an auditory oddball task. We associated fast, correct detection of certain auditory target stimuli with larger monetary rewards, and other auditory targets with smaller rewards. We found enhanced attentional processing of the more highly rewarded target stimuli, as evidenced by faster behavioral detection of those stimuli compared with lower-rewarded stimuli. Neurally, higher-reward associations enhanced the early sensory processing of auditory targets. Targets associated with higher-magnitude rewards had higher amplitude N1 and mismatch negativity (MMN) ERP components than targets associated with lower-magnitude rewards. Reward did not impact the latency of these early components. Higher-reward magnitude also decreased the latency and increased the amplitude of the longer-latency P3 component, suggesting that reward also can enhance the final processing stages of auditory target stimuli. These results provide insight into how the sensory and attentional neural processing of auditory stimuli is modulated by stimulus-reward associations and the magnitude of those associations, with higher-magnitude reward associations yielding enhanced auditory processing at both early and late stages compared with lower-magnitude reward associations.

No sound is more distracting than the one you're trying not to hear: delayed costs of mental control of task-irrelevant neutral and emotional sounds

Background

Suppressing intrusive thoughts can result in a post-suppression rebound effect where the same thoughts become hyperaccessible. The current study aimed to investigate if similar so-called rebound effects could be observed when people attempted to mentally suppress awareness of nonsensical auditory stimuli. Based on previous research on thought suppression and mental control in other domains, we hypothesized that attempting to suppress awareness of a task-irrelevant sound while under cognitive load would impact evaluations of the sound on affective dimensions and loudness, and result in increased general vigilance, as evidenced by faster responding on subsequent tasks.

Methods

We performed two experiments where participants in a suppression condition were initially instructed to mentally suppress awareness of a sound while performing a mentally challenging task. Participants in a control condition performed the same task without receiving any instructions regarding the sound. In Experiment 1, the sound was affectively neutral, while in Experiment 2 participants were presented with an inherently aversive (tinnitus-like) sound. After this initial phase, participants performed tasks measuring vigilance and attention, and were also asked to give subjective ratings of the sounds on a number of affective dimensions and loudness.

Results

In Experiment 1, participants in the suppression condition showed faster response times on both a visual search task and an auditory spatial cueing task, as compared to participants in the control condition. Contrary to our predictions, participants in the suppression condition did not rate the distractor sound as louder than participants in the control condition, and there were no differences on affective dimensions. In Experiment 2, results revealed that participants in the suppression condition made more errors on a visual search task, specifically on trials where the previously suppressed sound was presented. In contrast to results from Experiment 1, participants in the suppression condition also rated the targeted sound as louder.

Conclusions

The findings provide preliminary support for a post-suppression rebound effect in the auditory domain and further suggest that this effect may be moderated by the emotional properties of the auditory stimulus.

Value-Biased Competition in the Auditory System of the Brain

Attentional capture by previously reward-associated stimuli has predominantly been measured in the visual domain. Recently, behavioral studies of value-driven attention have demonstrated involuntary attentional capture by previously reward-associated sounds, emulating behavioral findings within the visual domain and suggesting a common mechanism of attentional capture by value across sensory modalities. However, the neural correlates of the modulatory role of learned value on the processing of auditory information has not been examined. Here, we conducted a neuroimaging study on human participants using a previously established behavioral paradigm that measures value-driven attention in an auditory target identification task. We replicate behavioral findings of both voluntary prioritization and involuntary attentional capture by previously reward-associated sounds. When task-relevant, the selective processing of high-value sounds is supported by reduced activation in the dorsal attention network of the visual system (FEF, intraparietal sulcus, right middle frontal gyrus), implicating cross-modal processes of biased competition. When task-irrelevant, in contrast, high-value sounds evoke elevated activation in posterior parietal cortex and are represented with greater fidelity in the auditory cortex. Our findings reveal two distinct mechanisms of prioritizing reward-related auditory signals, with voluntary and involuntary modes of orienting that are differently manifested in biased competition.

The past, present, and future of selection history

The last ten years of attention research have witnessed a revolution, replacing a theoretical dichotomy (top-down vs. bottom-up control) with a trichotomy (biased by current goals, physical salience, and selection history). This third new mechanism of attentional control, selection history, is multifaceted. Some aspects of selection history must be learned over time whereas others reflect much more transient influences. A variety of different learning experiences can shape the attention system, including reward, aversive outcomes, past experience searching for a target, target‒non-target relations, and more. In this review, we provide an overview of the historical forces that led to the proposal of selection history as a distinct mechanism of attentional control. We then propose a formal definition of selection history, with concrete criteria, and identify different components of experience-driven attention that fit within this definition. The bulk of the review is devoted to exploring how these different components relate to one another. We conclude by proposing an integrative account of selection history centered on underlying themes that emerge from our review.

How Does Threat Modulate the Motivational Effects of Reward on Attention?

Studies on attentional bias have overwhelmingly focused on the priority of different stimuli and have rarely manipulated the state of the observer. Recently, the threat of unpredictable shock has been utilized to experimentally induce anxiety and investigate how negative arousal modulates attentional control. Experimentally induced anxiety has been shown to reduce the attentional priority afforded to reward-related stimuli while enhancing the efficiency of goal-directed attentional control. It is unclear which of these two influences might dominate when attending to reward-related stimuli is consistent with task goals and by extension what the scope of the modulatory influence of threat on attention is. In contrast to paradigms in the visual domain, a novel auditory identification task has demonstrated a robust influence of target-value associations on selective attention. In the present study, we examined how the threat of shock modulates the influence of learned value on voluntary attention. In both threat and no-threat conditions, we replicate prior findings of voluntary prioritization of reward-associated sounds. However, unlike in studies measuring involuntary attentional capture, threat did not modulate the influence of reward on attention. Our findings highlight important limitations to when and how threat modulates the control of attention, contextualizing prior findings.

Disruptions of Sustained Spatial Attention Can Be Resistant to the Distractor's Prior Reward Associations

Attention can be involuntarily biased toward reward-associated distractors (value-driven attentional capture, VDAC). Yet past work has primarily demonstrated this distraction phenomenon during a particular set of circumstances: transient attentional orienting to potentially relevant stimuli occurring in our visual environment. Consequently, it is not well-understood if reward-based attentional capture can occur under other circumstances, such as during sustained visuospatial attention. Using EEG, we investigated whether associating transient distractors with reward value would increase their distractibility and lead to greater decrements in concurrent sustained spatial attention directed elsewhere. Human participants learned to associate three differently colored, laterally presented squares with rewards of varying magnitude (zero, small, and large). These colored squares were then periodically reintroduced as distractors at the same lateral locations during a demanding sustained-attention rapid-serial-visual-presentation (RSVP) task at the midline. Behavioral and neural evidence indicated that participants had successfully learned and maintained the reward associations to the distractors. During the RSVP task, consistent with prior work, we found that the distractors generated dips in the instantaneous amplitude of the steady-state visual evoked potentials (SSVEPs) elicited by the midline RSVP stimuli, indicating that the distractors were indeed transiently disrupting sustained spatial attention. Contrary to our hypotheses, however, the magnitude of this dip did not differ by the magnitude of the distractor’s reward associations. These results indicate that while sustained spatial attention can be impaired by the introduction of distractors at another location, the main distraction process is resistant to the distractors’ reward associations, thus providing evidence of an important boundary condition to value-driven attentional capture.

Previously reward-associated sounds interfere with goal-directed auditory processing

Previously reward-associated stimuli have consistently been shown to involuntarily capture attention in the visual domain. Although previously reward-associated but currently task-irrelevant sounds have also been shown to interfere with visual processing, it remains unclear whether such stimuli can interfere with the processing of task-relevant auditory information. To address this question, we modified a dichotic listening task to measure interference from task-irrelevant but previously reward-associated sounds. In a training phase, participants were simultaneously presented with a spoken letter and number in different auditory streams and learned to associate the correct identification of each of three letters with high, low, and no monetary reward, respectively. In a subsequent test phase, participants were again presented with the same auditory stimuli but were instead instructed to report the number while ignoring spoken letters. In both the training and test phases, response time measures demonstrated that attention was biased in favour of the auditory stimulus associated with high value. Our findings demonstrate that attention can be biased towards learned reward cues in the auditory domain, interfering with goal-directed auditory processing.

Cross-Modal Integration of Reward Value during Oculomotor Planning

Reward value guides goal-directed behavior and modulates early sensory processing. Rewarding stimuli are often multisensory, but it is not known how reward value is combined across sensory modalities. Here we show that the integration of reward value critically depends on whether the distinct sensory inputs are perceived to emanate from the same multisensory object. We systematically manipulated the congruency in monetary reward values and the relative spatial positions of co-occurring auditory and visual stimuli that served as bimodal distractors during an oculomotor task performed by healthy human participants (male and female). The amount of interference induced by the distractors was used as an indicator of their perceptual salience. Our results across two experiments show that when reward value is linked to each modality separately, the value congruence between vision and audition determines the combined salience of the bimodal distractors. However, the reward value of vision wins over the value of audition if the two modalities are perceived to convey conflicting information regarding the spatial position of the bimodal distractors. These results show that in a task that highly relies on the processing of visual spatial information, the reward values from multiple sensory modalities are integrated with each other, each with their respective weights. This weighting depends on the strength of prior beliefs regarding a common source for incoming unisensory signals based on their congruency in reward value and perceived spatial alignment.

Experience-Driven Auditory Attention

In addition to conscious goals and stimulus salience, an observer's prior experience also influences selective attention. Early studies demonstrated experience-driven effects on attention mainly in the visual modality, but increasing evidence shows that experience drives auditory selection as well. We review evidence for a multiple-levels framework of auditory attention, in which experience-driven attention relies on mechanisms that acquire control settings and mechanisms that guide attention towards selected stimuli. Mechanisms of acquisition include cue-target associative learning, reward learning, and sensitivity to prior selection history. Once acquired, implementation of these biases can occur either consciously or unconsciously. Future research should more fully characterize the sources of experience-driven auditory attention and investigate the neural mechanisms used to acquire and implement experience-driven auditory attention.

Involuntary sensory enhancement of gain- and loss-associated tones: A general relevance principle

In a recent event-related potential (ERP) study (Folyi et al., 2016), we have demonstrated that sensory processing of task-irrelevant tones is enhanced when they were previously associated with positive or negative (by the means of monetary gains and losses, respectively) affective meaning relative to tones with neutral meaning, as indexed by the enhancement of the auditory N1-amplitude. In the present study, (1) in line with the hypothesis of affective counter-regulation, we investigated whether positive versus negative tones can receive differential attentional enhancement, depending on motivational context (Experiment 1); and (2) whether the early facilitation of positive and negative tones can operate strictly outside of the focus of voluntary attention (Experiment 2). In Experiment 1, we replicated the basic N1 valence effect, but found no moderation by motivational context. In Experiment 2, we found a small valence effect on the N1. By combining data from the three experiments (i.e., our previous experiment and the present ones; N = 72), we found a clear enhancement of N1-amplitudes for valenced tones without moderation by experiment. This pattern of results suggests comparable early attentional enhancement of valenced tones in general: (a) despite different level of concurrent task-relevant attentional and motivational demands in these experiments; and (b) without prioritizing one valence category over another, supporting our claim that the general relevance of the tones with high motivational value that governs early attentional facilitation.

Neurobiology of value-driven attention

What we pay attention to is influenced by reward learning. Converging evidence points to the idea that associative reward learning changes how visual stimuli are processed in the brain, rendering learned reward cues difficult to ignore. Behavioral evidence distinguishes value-driven attention from other established control mechanisms, suggesting a distinct underlying neurobiological process. Recently, studies have begun to explore the neural substrates of this value-driven attention mechanism. Here, I review the progress that has been made in this area, and synthesize the findings to provide an integrative account of the neurobiology of value-driven attention. The proposed account can explain both attentional capture by previously rewarded targets and the modulatory effect of reward on priming, as well as the decoupling of reward history and prior task relevance in value-driven attention.

Selection history: How reward modulates selectivity of visual attention

Visual attention enables us to selectively prioritize or suppress information in the environment. Prominent models concerned with the control of visual attention differentiate between goal-directed, top-down and stimulus-driven, bottom-up control, with the former determined by current selection goals and the latter determined by physical salience. In the current review, we discuss recent studies that demonstrate that attentional selection does not need to be the result of top-down or bottom-up processing but, instead, is often driven by lingering biases due to the "history" of former attention deployments. This review mainly focuses on reward-based history effects; yet other types of history effects such as (intertrial) priming, statistical learning and affective conditioning are also discussed. We argue that evidence from behavioral, eye-movement and neuroimaging studies supports the idea that selection history modulates the topographical landscape of spatial "priority" maps, such that attention is biased toward locations having the highest activation on this map.