Misdirected by the gap: the relationship between inattentional blindness and attentional misdirection

In several of our articles we have drawn analogies between inattentional blindness paradigms and misdirection. Memmert (2010) however, has criticized this analogy and urged for caution in assuming too much of a close relationship between these two phenomena. Here we consider the points raised by Memmert and highlight some misunderstandings and omissions in his interpretation of our work, which substantially undermine his argument. Debating the similarities and differences between aspects of misdirection and inattentional blindness is valuable and has the potential to highlight the utility of these two phenomena. However, it is important not to be misdirected by subtle differences between particular instances of each phenomenon, at the expense of failing to detect the opportunities that these phenomena present for extending our understanding of attention and awareness.     

The role of perceptual load in inattentional blindness

Perceptual load theory offers a resolution to the long-standing early vs. late selection debate over whether task-irrelevant stimuli are perceived, suggesting that irrelevant perception depends upon the perceptual load of task-relevant processing. However, previous evidence for this theory has relied on RTs and neuroimaging. Here we tested the effects of load on conscious perception using the "inattentional blindness" paradigm. As predicted by load theory, awareness of a task-irrelevant stimulus was significantly reduced by higher perceptual load (with increased numbers of search items, or a harder discrimination vs. detection task). These results demonstrate that conscious perception of task-irrelevant stimuli critically depends upon the level of task-relevant perceptual load rather than intentions or expectations, thus enhancing the resolution to the early vs. late selection debate offered by the perceptual load theory.     

Visual distraction increases the detection of an unexpected object in inattentional blindness

Distraction is typically thought to be detrimental to performance and concentration, and stimuli are classified as “distractions” if they take attention away from a primary task. However it has been shown that, under certain circumstances, distractors can also improve task performance. The current study extends this literature by exploring the role of a single discrete transient visual distracting event in increasing attention to an unexpected visual object in an inattentional blindness (IB) paradigm. Experiment 1 investigated the impact of a 48 ms visual distraction stimulus on rates of IB; a second experiment used a shortened, 16 ms visual distracting event. Both the long 48 ms and brief 16 ms distractors significantly reduced overall IB rates, by approximately 50% compared to a no distractor condition. Moreover, this reduction in IB is obtained independent of whether the visual distracting event was noted by the observer. Our findings demonstrate that a single discrete visual distraction can improve the detectability of an unexpected object in an IB task. Implications for theories of distributed attention in such tasks are discussed.     

Pre-stimulus alpha predicts inattentional blindness

Pre- and post-stimulus oscillatory activity between 8 and 12 hertz, referred to as the alpha-band, correlates with conscious visual awareness of stimuli across a variety of psychophysical tasks. Within an EEG-adapted inattentional blindness task, the current study sought to examine whether this relationship holds for conscious awareness of stimuli under conditions of inattentional blindness. Noticing rates of the task-irrelevant unexpected stimulus were correlated with a significant decrease in alpha power over bilateral parietal-occipital areas during the pre-stimulus interval, and a significant decrease in alpha power over parietal-occipital regions in the right hemisphere during the post-stimulus interval. Findings are taken to imply alpha-band neural activity represents a valid correlate of consciousness that is not confounded by task relevancy or the need for report.     

Dissociation of processing time and awareness by the inattentional blindness paradigm

Consciousness researchers are interested in distinguishing between mental activity that occurs with and without awareness (i.e., explicit versus implicit processes). The inattentional blindness (IB) paradigm is an excellent tool for this question because it permits the independent manipulation of processing time and awareness. In the present study, we show that implicit texture segregation can occur during inattentional blindness, provided that the texture is exposed for a sufficient duration. In contrast, a Simon effect does not occur during inattentional blindness, even with similar exposure duration of the critical stimulus. This reveals a dissociation between processing time and awareness, consistent with the possibility of separate processing streams for explicit and implicit visual perception.     

Mind the gap: Misdirection, inattentional blindness and the relationship between overt and covert attention

The present commentary addresses two issues arising from Memmert’s (2010) paper. First, can the ‘misdirection’ and ‘inattentional blindness’ paradigms provide important insights into the relationship between ‘overt’ and ‘covert’ attentional processes? Second, what are the most fruitful directions for research that seeks to combine these attentional paradigms in ecologically valid settings? We argue that although Memmert’s (2010) paper postulates several important differences between the misdirection and inattentional blindness paradigms, it may not emphasise sufficiently strongly the significant insights into attention that have been yielded by the former approach. To illustrate, we discuss the utility of the misdirection paradigm in providing an ecologically valid method to investigate the relationship between overt and covert attentional processes. Such naturalistic methods are required to ensure optimal integration of the misdirection and inattentional blindness paradigms within a general theory of attention.     

Distance is relative: Inattentional blindness critically depends on the breadth of the attentional focus

Inattentional blindness – the phenomenon that we sometimes miss salient stimuli in our direct view when they appear unexpectedly and attention is focused on something else - is modulated by various parameters, including distance of the unexpected stimulus from the attentional focus. In two experiments, we expanded the existing literature on spatial factors influencing inattentional blindness as well as theories on the spatial distribution of attention. Noticing rates of unexpected objects were significantly higher when they appeared outside instead of inside the bounds of primary task stimuli. Thus, our results do neither support the account that spatial attention is tuned as a spotlight that includes relevant targets and everything in between nor an account of purely object-based attentional orientation. Instead, the results speak in favor of an inhibitory area between two attended targets. Experiment 2 replicated these surprising findings and additionally demonstrated that they were not confounded by task.     

The role of social meaning in inattentional blindness: When the gorillas in our midst do not go unseen

Without visual attention, even the obvious–like a gorilla walking through a scene of people–goes undetected (Mack & Rock, 1998; Simons & Chabris, 1999). This “inattentional blindness” is a persistent, well-documented limitation of the human visual system. The current research examines whether social meaning reduces this visual bias by imbuing unexpected objects with signal value, thus increasing their relevance and facilitating perception. Using one of the most established illustrations of inattentional blindness, we show for the first time that activating a social association, even an erroneous one (i.e., the African American–ape association), drastically attenuates inattentional blindness. This is not accounted for by visual feature matching. Rather, these results suggest that social meaning, even when flawed, may direct our visual system towards associated visual information that would otherwise be overlooked. As such, these results provide a powerful replication of the African American–ape association and illustrate that this broadly held association has the power to spontaneously change the content of one's visual world.     

Independence between implicit and explicit processing as revealed by the Simon effect

Studies showing human behavior influenced by subliminal stimuli mainly focus on implicit processing per se, and little is known about its interaction with explicit processing. We examined this by using the Simon effect, wherein a task-irrelevant spatial distracter interferes with lateralized response. Lo and Yeh (2008) found that the visual Simon effect, although it occurred when participants were aware of the visual distracters, did not occur with subliminal visual distracters. We used the same paradigm and examined whether subliminal and supra-threshold stimuli are processed independently by adding a supra-threshold auditory distracter to ascertain whether it would interact with the subliminal visual distracter. Results showed auditory Simon effect, but there was still no visual Simon effect, indicating that supra-threshold and subliminal stimuli are processed separately in independent streams. In contrast to the traditional view that implicit processing precedes explicit processing, our results suggest that they operate independently in a parallel fashion.     

The gap between inattentional blindness and attentional misdirection

Kuhn and colleagues described a novel attentional misdirection approach (deliberate diversion of attention away from a visually salient stimulus) to investigate overt and covert attention mechanisms in connection with inattentional blindness (not being able to perceive something that is plainly visible because one’s attention has not been focused on it). This misdirection paradigm is valuable to study the temporal relationship between eye movements and visual awareness. Although, as put forth in this comment, the link between attentional misdirection and inattentional blindness needs to be developed further. There are at least four differences between the two paradigms which concern the conceptual aspects of the unexpected object and the methodological aspects of the task design. This highlights the need for a broader theoretical framework incorporating inattentional blindness and overt and covert attention mechanisms. Two possible research lines focusing on the orienting attention research and the “selection-for-action” paradigm are discussed.     

The unexpected killer: effects of stimulus threat and negative affectivity on inattentional blindness

Inattentional blindness (IB) occurs when observers fail to detect unexpected objects or events. Despite the adaptive importance of detecting unexpected threats, relatively little research has examined how stimulus threat influences IB. The current study was designed to explore the effects of stimulus threat on IB. Past research has also demonstrated that individuals with elevated negative affectivity have an attentional bias towards threat-related stimuli; therefore, the current study also examined whether state and trait levels of negative affectivity predicted IB for threat-related stimuli. One hundred and eleven participants (87 female, aged 17–40 years) completed an IB task that included both threat-related and neutral unexpected stimuli, while their eye movements were tracked. Participants were significantly more likely to detect the threatening stimulus (19%) than the neutral stimulus (11%) p = .035, odds ratio (OR) = 4.0, 95% confidence interval OR [1.13, 14.17]. Neither state nor trait levels of negative affectivity were significantly associated with IB. These results suggest observers are more likely to detect threat-related unexpected objects, consistent with the threat superiority effect observed in other paradigms. However, most observers were blind to both unexpected stimuli, highlighting the profound influence of expectations and task demands on our ability to perceive even potentially urgent and life-threatening information.     

The developmental difference of inattentional blindness in 3-to-5-year-old preschoolers and its relationship with fluid intelligence

Preschoolers can focus on the events that they are interested in and shield other information that may still be obvious and important, and this phenomenon is termed as inattentional blindness (IB). The present study investigated the developmental differences in IB and explored its relationship with fluid intelligence in 3-to-5-year-old preschoolers. With the involvement of one hundred and thirty-five preschoolers, it was found that the IB rates decreased with age during 3-to-5-year-olds. Fluid intelligence could significantly predict the incidence of IB in 4-year-olds, which means that those with higher fluid intelligence scores experience less IB. It implied that the ability to detect unintentional stimuli increased from 3-to-5-year-olds, whereas age was an impact factor to the relationship between fluid intelligence and IB.     

Attentional biases in social anxiety: an investigation using the inattentional blindness paradigm

One line of research has examined attentional bias as a potential maintenance factor in social anxiety using cognitive experiment paradigms. The present study sought to examine the utility of the inattentional blindness (IB) paradigm for assessing attentional bias in social anxiety. Unlike other existing paradigms such as the emotional Stroop or dot-probe tasks, the IB paradigm has the advantage of eliminating the individual's expectation and intention to search for social cues, which would reduce strategic or effortful responses. Two independent experiments were conducted using college students scoring high or low on the Fear of Negative Evaluation Scale. In both Experiments 1 and 2, participants were randomized to one of three IB experiment conditions, in which a positive face, a negative face, or a neutral item was unexpectedly presented, in the presence/absence of a bogus-speech threat. The overall pattern of our data suggests the presence of hypervigilant attentional processing in social anxiety. The IB paradigm appears to be a useful addition to existing experiment paradigms for investigating attentional bias in social anxiety and perhaps other psychopathology.     

Release of inattentional blindness by high working memory load: elucidating the relationship between working memory and selective attention

An unexpected stimulus often remains unnoticed if attention is focused elsewhere. This inattentional blindness has been shown to be increased under conditions of high memory load. Here we show that increasing working memory load can also have the opposite effect of reducing inattentional blindness (i.e., improving stimulus detection) if stimulus detection is competing for attention with a concurrent visual task. Participants were required to judge which of two lines was the longer while holding in working memory either one digit (low load) or six digits (high load). An unexpected visual stimulus was presented once alongside the line judgment task. Detection of the unexpected stimulus was significantly improved under conditions of higher working memory load. This improvement in performance prompts the striking conclusion that an effect of cognitive load is to increase attentional spread, thereby enhancing our ability to detect perceptual stimuli to which we would normally be inattentionally blind under less taxing cognitive conditions. We discuss the implications of these findings for our understanding of the relationship between working memory and selective attention.     

Examining effects of preconscious mere exposure: An inattentional blindness approach

An increase in affective preference for stimuli, which a person has been repeatedly exposed to, is known as mere exposure effect. This effect has been shown for stimuli that are processed subliminally, that is, below the threshold of awareness. This study fills a current research gap by investigating mere exposure effects under processing that is preconscious, which follows from a high stimulus strength but absence of top-down amplification. In three experiments (N = 240 in total) preconscious processing was evoked using an inattentional blindness paradigm, which allowed the processing of stimuli (nonwords or Chinese symbols) under complete inattention. Contrary to our hypothesis, we did not find a mere exposure effect in our experiments. We expand the current state of knowledge by discussing the distractor devaluation effect and the attentional set of participants as possible reasons for the absence of the mere exposure effect. Directions for future investigations are outlined.     

Inhibition of return exaggerates change blindness

Peripheral cues trigger attention shifts, which facilitate perceptual processing and enhance visual awareness. However, this facilitation is superseded by an inhibition of return (IOR) effect, which biases attention away from the cued location. While the link between facilitatory effects of visual attention and awareness is well established, no study has reported negative effects of spatial cueing on visual awareness. This failure is puzzling, given the claim that attention is a necessary precondition for awareness. If attention is necessary for awareness, inhibiting attention should also inhibit awareness. This leads to a slightly counterintuitive prediction: Spatial cueing will inhibit awareness at long cue–target latencies. This study shows that subliminal peripheral cues exaggerate change blindness at long cue–change latencies, demonstrating that IOR can suppress visual awareness of changes and suggesting that IOR can directly affect the contents of consciousness.     

High perceptual load causes inattentional blindness and deafness in drivers

ABSTRACT

Perceptual load theory of attention predicts that the level of perceptual load in a primary task affects the processing of additional stimuli. Given the lack of ecologically valid evidence for the model, the current study assessed the effect of perceptual load on driver awareness during simulated driving tasks. The results showed that perceptual load dramatically affected driver awareness for visual and auditory stimuli, even those that were driving relevant and safety critical (e.g. pedestrians or the sound of a car horn). The results support load theory and suggest that perceptual load may be an important factor in driver safety.     

ERP signatures of conscious and unconscious word and letter perception in an inattentional blindness paradigm

A three-phase inattentional blindness paradigm was combined with ERPs. While participants performed a distracter task, line segments in the background formed words or consonant-strings. Nearly half of the participants failed to notice these word-forms and were deemed inattentionally blind. All participants noticed the word-forms in phase 2 of the experiment while they performed the same distracter task. In the final phase, participants performed a task on the word-forms. In all phases, including during inattentional blindness, word-forms elicited distinct ERPs during early latencies (∼200–280 ms) suggesting unconscious orthographic processing. A subsequent ERP (∼320–380 ms) similar to the visual awareness negativity appeared only when subjects were aware of the word-forms, regardless of the task. Finally, word-forms elicited a P3b (∼400–550 ms) only when these stimuli were task-relevant. These results are consistent with previous inattentional blindness studies and help distinguish brain activity associated with pre- and post-perceptual processing from correlates of conscious perception.     

The role of attention in subitizing

The process of rapidly and accurately enumerating small numbers of items without counting, i.e. subitizing, is often believed to rest on parallel preattentive processes. However, the possibility that enumeration of small numbers of items would also require attentional processes has remained an open question. The present study is the first that directly contrasts the preattentive and attentive models of subitizing. We used an inattentional blindness paradigm to manipulate the availability of attentional resources during enumeration. In the inattention condition, the items to be enumerated were presented unexpectedly while participants focused on a line length comparison task. Divided- and full-attention conditions were also included. The results showed that only numbers one and two could be enumerated when the effects of attention were minimized. Freeing attentional resources increased the enumeration accuracies considerably, including for number two. The results suggest that even for enumerating small numbers, the attentional demands increase as the number of objects increases.