Priming makes a stimulus more salient

Does cross-modal correspondence modulate modality-specific perceptual processing? Study using timing judgment tasks

Cross-modal correspondences refer to associations between stimulus features across sensory modalities. Previous studies have shown that cross-modal correspondences modulate reaction times for detecting and identifying stimuli in one modality when uninformative stimuli from another modality are present. However, it is unclear whether such modulation reflects changes in modality-specific perceptual processing. We used two psychophysical timing judgment tasks to examine the effects of audiovisual correspondences on visual perceptual processing. In Experiment 1, we conducted a temporal order judgment (TOJ) task that asked participants to judge which of two visual stimuli presented with various stimulus onset asynchronies (SOAs) appeared first. In Experiment 2, we conducted a simultaneous judgment (SJ) task that asked participants to report whether the two visual stimuli were simultaneous or successive. We also presented an unrelated auditory stimulus, simultaneously or preceding the first visual stimulus, and manipulated the congruency between audiovisual stimuli. Experiment 1 indicated that the points of subjective simultaneity (PSSs) between the two visual stimuli estimated in the TOJ task shifted according to the audiovisual correspondence between the auditory pitch and visual features of vertical location and size. However, these audiovisual correspondences did not affect PSS estimated using the SJ task in Experiment 2. The different results of the two tasks can be explained through the response bias triggered by audiovisual correspondence that only the TOJ task included. We concluded that audiovisual correspondence would not modulate visual perceptual timing and that changes in modality-specific perceptual processing might not trigger the congruency effects reported in previous studies.

No evidence for spatial suppression due to across-trial distractor learning in visual search

Previous studies have shown that during visual search, participants are able to implicitly learn across-trial regularities regarding target locations and use these to improve search performance. The present study asks whether such across-trial visual statistical learning also extends to the location of salient distractors. In Experiments 1 and 2, distractor regularities were paired so that a specific distractor location was 100% predictive of another specific distractor location on the next trial. Unlike previous findings that employed target regularities, the current results show no difference in search times between predictable and unpredictable trials. In Experiments 3-5 the distractor location was presented in a structured order (a sequence) for one group of participants, while it was presented randomly for the other group. Again, there was no learning effect of the across-trial regularities regarding the salient distractor locations. Across five experiments, we demonstrated that participants were unable to exploit across-trial spatial regularities regarding the salient distractors. These findings point to important boundary conditions for the modulation of visual attention by statistical regularities and they highlight the need to differentiate between different types of statistical regularities.

Priming effects in inefficient visual search: Real, but transient

In visual search tasks, responses to targets on one trial can influence responses on the next trial. Most typically, target repetition speeds response while switching to a different target slows response. Such “priming” effects have sometimes been given very significant roles in theories of search (e.g., Theeuwes, Philosophical Transactions of the Royal Society B: Biological Sciences, 368, 1628, 2013). Most work on priming has involved “singleton” or “popout” tasks. In non-popout priming tasks, observers must often perform a task-switching operation because the guiding template for one target (e.g., a red vertical target in a conjunction task) is incompatible with efficient search for the other target (green horizontal, in this example). We examined priming in inefficient search where the priming feature (Color: Experiments 1–3, Shape: Experiments 4–5) was irrelevant to the task of finding a T among Ls. We wished to determine if finding a red T on one trial helped observers to be more efficient if the next T was also red. In all experiments, we found additive priming effects. The reaction time (RT) for the second trial was shorter if the color of the T was repeated. However, there was no interaction with set size. The slope of the RT × Set Size function was not shallower for runs of the same target color, compared to trials where the target color switched. We propose that priming might produce transient guidance of the earliest deployments of attention on the next trial or it might speed decisions about a selected target. Priming does not appear to guide attention over the entire search.

Pitch-elevation and pitch-size cross-modal correspondences do not affect temporal ventriloquism

Temporal ventriloquism refers to the shift in the perceived timing of a visual stimulus towards a transient auditory stimulus presented close in time. This effect is demonstrated by greater sensitivity of temporal order judgments of two visual stimuli when a sound is presented before the first visual stimulus and after the second visual stimulus. Recent studies suggest that temporal ventriloquism is affected by cross-modal correspondence between auditory pitch and visual elevation but not by correspondence between pitch and visual size. Here we examined the possibility that these results do not reflect a difference in the effects of different types of cross-modal correspondences on temporal ventriloquism but are rather mediated by shifts in visual-spatial attention triggered by preceding auditory stimuli. In Experiment 1, we replicated the results of previous studies that varied with the type of correspondence. Experiment 2 investigated the effects of the second audiovisual stimuli's asynchrony while the first audiovisual stimuli were synchronized. The results, unlike in Experiment 1, revealed that the magnitude of the temporal ventriloquism effect did not change with the congruency of pitch-elevation correspondence. Experiment 3 also indicated that the asynchrony of the first audiovisual stimuli modulated visual discrimination sensitivity irrespective of temporal ventriloquism. These results suggest that cross-modal correspondences do not affect temporal ventriloquism. Greater visual sensitivity when audiovisual stimuli are congruent with pitch-elevation correspondence may be attributable to shifts in visual attention caused by pitches of the preceding auditory stimulus, which speeds up detection of the first visual stimulus.

Does feature intertrial priming guide attention? The jury is still out

Our search performance is strongly influenced by our past experience. In the lab, this influence has been demonstrated by investigating a variety of phenomena, including intertrial priming, statistical learning, and reward history, and collectively referred to as selection history. The resulting findings have led researchers to claim that selection history guides attention, thereby challenging the prevailing dichotomy, according to which top-down and bottom-up factors alone determine attentional priority. Here, we re-examine this claim with regard to one selection-history phenomenon, feature intertrial priming (aka priming of pop-out). We evaluate the evidence that specifically pertains to the role of feature intertrial priming in attentional guidance, rather than in later selective processes occurring after the target is found. We distinguish between the main experimental rationales, while considering the extent to which feature intertrial priming, as studied through different protocols, shares characteristics of top-down attention. We show that there is strong evidence that feature intertrial priming guides attention when the experimental protocol departs from the canonical paradigm and encourages observers to maintain the critical feature in visual working memory or to form expectations about the upcoming target. By contrast, the current evidence regarding the standard feature intertrial priming phenomenon is inconclusive. We propose directions for future research and suggest that applying the methodology used here in order to re-evaluate of the role of other selection history phenomena in attentional guidance should clarify the mechanisms underlying the strong impact of past experience on visual search performance.

Alpha-Band Phase Modulates Bottom-up Feature Processing

Recent studies reveal that attention operates in a rhythmic manner, that is, sampling each location or feature alternatively over time. However, most evidence derives from top-down tasks, and it remains elusive whether bottom-up processing also entails dynamic coordination. Here, we developed a novel feature processing paradigm and combined time-resolved behavioral measurements and electroencephalogram (EEG) recordings to address the question. Specifically, a salient color in a multicolor display serves as a noninformative cue to capture attention and presumably reset the oscillations of feature processing. We then measured the behavioral performance of a probe stimulus associated with either high- or low-salient color at varied temporal lags after the cue. First, the behavioral results (i.e., reaction time) display an alpha-band (~8 Hz) profile with a consistent phase lag between high- and low-salient conditions. Second, simultaneous EEG recordings show that behavioral performance is modulated by the phase of alpha-band neural oscillation at the onset of the probes. Finally, high- and low-salient probes are associated with distinct preferred phases of alpha-band neural oscillations. Taken together, our behavioral and neural results convergingly support a central function of alpha-band rhythms in feature processing, that is, features with varied saliency levels are processed at different phases of alpha neural oscillations.

Differential color tuning of the mesolimbic reward system

Visual wavelengths are not only associated with the subjective experience of color but also have long been thought to regulate affect. Here we examined the attracting rewarding properties of opposite ends of the wavelength spectrum, as well as their individual variation. As reward is multifaceted, we sought convergent evidence from subjective and objective behavioral and attentional indices, as well as its neural reward system bases. On average, short (blue) relative to long (red) wavelengths were judged subjectively more pleasant and had objectively greater behavioral and attentional salience, regulating speed of simple color discriminations and perception of temporal order. Consistent with reward, these color effects were magnified following monetary reinforcement. Pronounced individual differences in color effects were related to reward but not punishment sensitivity, with blue relative to red preference associated with high relative to low reward sensitivity. An fMRI study revealed these individual differences were supported by color-dependent functional coupling between the visual cortices and mesolimbic reward circuitry. Our findings reveal the reward bases of color, demonstrating color is a potent regulator of perception, action, and neural dynamics.

Implicitly and explicitly encoded features can guide attention in free viewing

It is well known that priming, probably by the contents of working memory, can influence subsequent visual task performance. How ubiquitous is this effect? Can incidental exposure to visual stimuli influence the deployment of attention when there is no explicit visual task? Results of two experiments show that a preceding stimulus can influence free-viewing eye movements. A simple change detection task was used as the cover task. The initial memory display was the priming display, while subsequent filler display constituted the free-viewing display of our interest. In Experiment 1, subjects were asked to memorize the number of items in the priming display. Subjects were not explicitly instructed to attend to features, but these might still be implicitly encoded. In Experiment 2, a more complex change detection task required subjects to memorize the number, color, and shape of priming items. Here, prime features were attended and, presumably, explicitly encoded. We were interested to know whether incidentally or explicitly encoded features of prime items would influence attention distribution in the filler display. In both experiments, items sharing color and shape with the prime were attended more often than predicted by chance. Items sharing neither color nor shape were attended less often. Items sharing either color or shape (not both) could also attract attention showing that the priming need not be based on a bound representation of the primed item. Effects were stronger in Experiment 2. No intention or top-down control appears to be needed to produce this priming.

Learned prioritization yields attentional biases through selection history

While numerous studies have provided evidence for selection history as a robust influence on attentional allocation, it is unclear precisely which behavioral factors can result in this form of attentional bias. In the current study, we focus on “learned prioritization” as an underlying mechanism of selection history and its effects on selective attention. We conducted two experiments, each starting with a training phase to ensure that participants learned different stimulus priorities. This was accomplished via a visual search task in which a specific color was consistently more relevant when presented together with another given color. In Experiment 1, one color was always prioritized over another color and inferior to a third color, such that each color had an equal overall priority by the end of the training session. In Experiment 2, the three different colors had unequal priorities at the end of the training session. A subsequent testing phase in which participants had to search for a shape-defined target showed that only stimuli with unequal overall priorities (Experiment 2) affected attentional selection, with increased reaction times when a distractor was presented in a previously high-priority compared with a low-priority color. These results demonstrate that adopting an attentional set where certain stimuli are prioritized over others can result in a lingering attentional bias and further suggest that selection history does not equally operate on all previously selected stimuli. Finally, we propose that findings in value-driven attention studies where high-value and low-value signaling stimuli differentially capture attention may be a result of learned prioritization rather than reward.

Yellow is for safety: perceptual and affective perspectives

Is there a link between color and safety? Yellow is often used in safety contexts. Using the Singapore accident record datasets, Ho et al. provided evidence that yellow taxis have fewer accidents than blue taxis (Ho et al. in Proc Natl Acad Sci 114(12):3074-3078, 2017). Does yellow differentially influence attention and action and if so is this related to purely visual or affective factors? Here, we examined the visual priority of yellow relative to luminance matched colors at opposing ends of the wavelength spectrum (i.e., red and blue), using a temporal order judgment task, between color pairs. Despite being matched in arousal, when yellow and blue were pitted against each other, yellow was consistently seen as occurring first, even when objectively appearing second at short stimulus onset asynchronies. Despite being matched in valence, yellow again showed a larger temporal priority when it was pitted against red. Yellow temporal priority bias was modulated by individual differences in regulatory focus, highlighting a potential affective-motivational origin. These results support that yellow is a safety color, having a temporal advantage, and further evidence that colors have special influences on cognition, perception and behavior.

All-or-None Context Dependence Delineates Limits of FEF Visual Target Selection

Choices of where to look are informed by perceptual judgments, which locate objects of current value or interest within the visual scene. This perceptual-motor transform is partly implemented in the frontal eye field (FEF), where visually responsive neurons appear to select behaviorally relevant visual targets and, subsequently, saccade-related neurons select the movements required to look at them. Here, we use urgent decision-making tasks to show (1) that FEF motor activity can direct accurate, visually informed choices in the complete absence of prior target-distracter discrimination by FEF visual responses and (2) that such discrimination by FEF visual cells shows an all-or-none reliance on the presence of stimulus attributes strongly associated with saliency-driven attentional allocation. The present findings suggest that FEF visual target selection is specific to visual judgments made on the basis of saliency and may not play a significant role in guiding saccadic choices informed solely by feature content.

Differential temporal salience of earning and saving

People are often characterized as poor savers. Here we examined whether cues associated with earning and saving have differential salience for attention and action. We first modeled earning and saving after positive and negative variants of monetary reinforcement, i.e., gains versus avoiding loss. Despite their equivalent absolute magnitude in a monetary incentive task, colors predicting saving were judged to appear after those that predicted earning in a temporal-order judgment task. This saving posteriority effect also occurred when savings were framed as earnings that come slightly later. Colors predicting savings, whether they acquired either negative or positive value, persisted in their posteriority. An attentional asymmetry away from money-saved relative to money-earned, potentially contributes to decreased everyday salience and future wealth.

Economists have observed that many people seem unwilling to save for the future. Here, the authors show that earning and saving are subject to a basic asymmetry in attentional choice, such that cues that are associated with saving are perceived as occurring later than cues associated with earning.

Visual Selection: Usually Fast and Automatic; Seldom Slow and Volitional

Recently it was argued that in addition to top-down and bottom-up processes, lingering biases of selection history play a major role in visual selection (Awh, Belopolsky & Theeuwes, 2012). Since its publication there has been a growing controversy about the terms top-down, bottom-up and selection-history in relation to visual selection. In the current paper we define these terms, discuss some controversies about these terms and explain what kind of effects should be considered to be the result of lingering biases of selection history, i.e., priming, reward/fear, and statistical learning. We discuss the properties of top-down selection (slow, effortful, and controlled) versus the properties of lingering biases of selection history (fast, effortless, and automatic). We adhere the position that the experience with selecting a particular feature or the location of a feature, may boost and sharpen its representation within the priority selection map above and beyond its physical salience. It is as if the experience may render a feature or location subjectively more salient. Our message of the current review is that true top-down control of visual selection occurs far less often than what is typically assumed. Most of the time, selection is based on experience and history. It is fast, automatic and occurs without much, if any, effort.

Reward priming eliminates color-driven affect in perception

Brain and behavior evidence suggests that colors have distinct affective properties. Here, we investigated how reward influences color-driven affect in perception. In Experiment 1, we assessed competition between blue and red patches during a temporal-order judgment (TOJ) across a range of stimulus onset asynchronies (SOAs). During the value reinforcement, reward was linked to either blue (version 1) or red (version 2) in the experiment. The same stimuli then served as test ones in the following unrewarded, unspeeded TOJ task. Our analysis showed that blue patches were consistently seen as occurring first, even when objectively appearing 2nd at short SOAs. This accelerated perception of blue over red was disrupted by prior primes related to reward (vs. neutral) but not perceptional (blue vs. red) priming. Experiment 2 replicated the findings of Experiment 1 while uncoupling action and stimulus values. These results are consistent with the blue-approach and red-avoidance motivation hypothesis and highlight an active nature of the association of reward priming and color processing. Together, the present study implies a link between reward and color affect and contributes to the understanding of how reward influences color affect in visual processing.

Learned value and object perception: Accelerated perception or biased decisions?

Learned value is known to bias visual search toward valued stimuli. However, some uncertainty exists regarding the stage of visual processing that is modulated by learned value. Here, we directly tested the effect of learned value on preattentive processing using temporal order judgments. Across four experiments, we imbued some stimuli with high value and some with low value, using a nonmonetary reward task. In Experiment 1, we replicated the value-driven distraction effect, validating our nonmonetary reward task. Experiment 2 showed that high-value stimuli, but not low-value stimuli, exhibit a prior-entry effect. Experiment 3, which reversed the temporal order judgment task (i.e., reporting which stimulus came second), showed no prior-entry effect, indicating that although a response bias may be present for high-value stimuli, they are still reported as appearing earlier. However, Experiment 4, using a simultaneity judgment task, showed no shift in temporal perception. Overall, our results support the conclusion that learned value biases perceptual decisions about valued stimuli without speeding preattentive stimulus processing.

Feature singletons attract spatial attention independently of feature priming

People perform better in visual search when the target feature repeats across trials (intertrial feature priming [IFP]). Here, we investigated whether repetition of a feature singleton's color modulates stimulus-driven shifts of spatial attention by presenting a probe stimulus immediately after each singleton display. The task alternated every two trials between a probe discrimination task and a singleton search task. We measured both stimulus-driven spatial attention (via the distance between the probe and singleton) and IFP (via repetition of the singleton's color). Color repetition facilitated search performance (IFP effect) when the set size was small. When the probe appeared at the singleton's location, performance was better than at the opposite location (stimulus-driven attention effect). The magnitude of this attention effect increased with the singleton's set size (which increases its saliency) but did not depend on whether the singleton's color repeated across trials, even when the previous singleton had been attended as a search target. Thus, our findings show that repetition of a salient singleton's color affects performance when the singleton is task relevant and voluntarily attended (as in search trials). However, color repetition does not affect performance when the singleton becomes irrelevant to the current task, even though the singleton does capture attention (as in probe trials). Therefore, color repetition per se does not make a singleton more salient for stimulus-driven attention. Rather, we suggest that IFP requires voluntary selection of color singletons in each consecutive trial.

Auditory frequency perception adapts rapidly to the immediate past

Frequency modulation is critical to human speech. Evidence from psychophysics, neurophysiology, and neuroimaging suggests that there are neuronal populations tuned to this property of speech. Consistent with this, extended exposure to frequency change produces direction specific aftereffects in frequency change detection. We show that this aftereffect occurs extremely rapidly, requiring only a single trial of just 100-ms duration. We demonstrate this using a long, randomized series of frequency sweeps (both upward and downward, by varying amounts) and analyzing intertrial adaptation effects. We show the point of constant frequency is shifted systematically towards the previous trial's sweep direction (i.e., a frequency sweep aftereffect). Furthermore, the perception of glide direction is also independently influenced by the glide presented two trials previously. The aftereffect is frequency tuned, as exposure to a frequency sweep from a set centered on 1,000 Hz does not influence a subsequent trial drawn from a set centered on 400 Hz. More generally, the rapidity of adaptation suggests the auditory system is constantly adapting and "tuning" itself to the most recent environmental conditions.

Assessing the effect of a true-positive recall case in screening mammography: does perceptual priming alter radiologists' performance?

OBJECTIVE

To measure the effect of the insertion of less-difficult malignant cases on subsequent breast cancer detection by breast imaging radiologists.

METHODS

The research comprises two studies. Study 1: 8 radiologists read 2 sets of images each consisting of 40 mammographic cases. Set A contained four abnormal cases, and Set B contained six abnormal cases, including two priming cases (less difficult malignancies) placed at intervals of three and five subsequent cases before a subtle cancer. Study 2: 16 radiologists read a third condition of the same cases, known as Set C, containing six abnormal cases and two priming cases immediately preceding the subtle cancer cases. The readers were asked to localize malignancies and give confidence ratings on decisions.

RESULTS

Although not significant, a decrease in performance was observed in Set B compared with in Set A. There was a significant increase in the receiver operating characteristic (ROC) area under the curve (z = -2.532; p = 0.0114) and location sensitivity (z = -2.128; p = 0.0333) between the first and second halves of Set A and a marginal improvement in jackknife free-response ROC figure of merit (z = -1.89; p = 0.0587) between the first and second halves of Set B. In Study 2, Set C yielded no significant differences between the two halves of the study.

CONCLUSION

Overall findings show no evidence that priming with lower difficulty malignant cases affects the detection of higher difficulty cancers; however, performance may decrease with priming.

ADVANCES IN KNOWLEDGE

This research suggests that inserting additional malignant cases in screening mammography sets as an audit tool may potentially lead to a decrease in performance of experienced breast radiologists.