Seeing, Sensing, and Scrutinizing

Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this <i>change blindness</i> can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, and to cast new light on the way that it is—and is not—involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of <i>seeing</i>. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a <i>virtual representation</i>, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This <i>sensing</i> is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself—the mechanisms involved when <i>scrutinizing</i> items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved

Individual differences in change blindness are predicted by the strength and stability of visual representations

The phenomenon of change blindness reveals that people are surprisingly poor at detecting unexpected visual changes; however, research on individual differences in detection ability is scarce. Predictive processing accounts of visual perception suggest that better change detection may be linked to assigning greater weight to prediction error signals, as indexed by an increased alternation rate in perceptual rivalry or greater sensitivity to low-level visual signals. Alternatively, superior detection ability may be associated with robust visual predictions against which sensory changes can be more effectively registered, suggesting an association with high-level mechanisms of visual short-term memory (VSTM) and attention. We administered a battery of 10 measures to explore these predictions and to determine, for the first time, the test–retest reliability of commonly used change detection measures. Change detection performance was stable over time and generalized from displays of static scenes to video clips. An exploratory factor analysis revealed two factors explaining performance across the battery, that we identify as visual stability (loading on change detection, attention measures, VSTM and perceptual rivalry) and visual ability (loading on iconic memory, temporal order judgments and contrast sensitivity). These results highlight the importance of strong, stable representations and the ability to resist distraction, in order to successfully incorporate unexpected changes into the contents of visual awareness

Attentional Modulation of Change Detection ERP Components by Peripheral Retro-Cueing

Change detection is essential for visual perception and performance in our environment. However, observers often miss changes that should be easily noticed. A failure in any of the processes involved in conscious detection (encoding the pre-change display, maintenance of that information within working memory, and comparison of the pre and post change displays) can lead to change blindness. Given that unnoticed visual changes in a scene can be easily detected once attention is drawn to them, it has been suggested that attention plays an important role on visual awareness. In the present study, we used behavioral and electrophysiological (ERPs) measures to study whether the manipulation of retrospective spatial attention affects performance and modulates brain activity related to the awareness of a change. To that end, exogenous peripheral cues were presented during the delay period (retro-cues) between the first and the second array using a one-shot change detection task. Awareness of a change was associated with a posterior negative amplitude shift around 228–292 ms (“Visual Awareness Negativity”), which was independent of retrospective spatial attention, as it was elicited to both validly and invalidly cued change trials. Change detection was also associated with a larger positive deflection around 420–580 ms (“Late Positivity”), but only when the peripheral retro-cues correctly predicted the change. Present results confirm that the early and late ERP components related to change detection can be functionally dissociated through manipulations of exogenous retro-cueing using a change blindness paradigmThis work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) grant PSI2014-53743-PS

Activity in the Visual Cortex is Modulated by Top-Down Attention Locked to Reaction Time

We studied the correlation between perception and hemodynamic activity in the visual cortex in a change detection task. Whenever the observer perceived the location of a change, rightly or wrongly, the blood oxygenation level-dependent signal increased in the primary visual cortex and the nearby extrastriate areas above the baseline activity caused by the visual stimulation. This non-sensory-evoked activity was localized and corresponded to the perceived location of the change. When a change was missed, or when observers attended to a different task, the change failed to evoke such a response. The latency of the nonsensory component increased linearly with subjects' reaction time, with a slope of one, and its amplitude was independent of contrast. Control experiments are compatible with the hypothesis that the nonsensory hemodynamic signal is mediated by top-down spatial attention, linked to (but separate from) awareness of the change

Pip and Pop: When auditory alarms facilitate visual change detection in dynamic settings

Dynamic and complex command and control situations often require the timely recognition of changes in the environment in order to detect potentially malicious actions. Change detection can be challenging within a continually evolving scene, and particularly under multitasking conditions whereby attention is necessarily divided between several subtasks. On-screen tools can assist with detection (e.g., providing a visual record of changes, ensuring that none are overlooked), however, in a high workload environment, this may result in information overload to the detriment of the primary task. One alternative is to exploit the auditory modality as a means to support visual change detection. In the current study, we use a naval air-warfare simulation, and introduce an auditory alarm to coincide with critical visual changes (in aircraft speed/direction) on the radar. We found that participants detected a greater percentage of visual changes and were significantly quicker to detect these changes when they were accompanied by an auditory alarm than when they were not. Furthermore, participants reported that mental demand was lower in the auditory alarm condition, and this was reflected in reduced classification omissions on the primary task. Results are discussed in relation to Wickens’ multiple resource theory of attention and indicate the potential for using the auditory modality to facilitate visual change detection

Crossmodal Load and Selective Attention

This thesis explores a current dominant theory of attention - the load theory of selective attention and cognitive control (Lavie et al., 2004). Load theory has been posited as a potential resolution to the long-running debate over the locus of selection in attention. Numerous studies confirm that high visual perceptual load in a relevant task leads to reduced interference from task-relevant distractors; whereas high working memory load leads to increased interference from task-irrelevant distractors in a relevant task. However, very few studies have directly tested perceptual and working memory load effects on the processing of task-relevant stimuli, and even fewer studies have tested the impact of load on processing both within and between different sensory modalities. This thesis details several novel experiments that test both visual and auditory perceptual and working memory load effects on task-relevant change detection in a change-blindness “flicker” task. Results indicate that both high visual and auditory perceptual load can impact on change detection, which implies that the perceptual load model can account for load effects on change detection, both within and between different sensory modalities. Results also indicate that high visual working memory load can impact on change detection. By contrast, high auditory working memory load did not appear to impact change detection. These findings do not directly challenge load theory per-se, but instead highlight how working memory load can have markedly different effects in different experimental paradigms. The final part of this thesis explores whether high perceptual load can attenuate distraction from highly emotionally salient stimuli. The findings suggest that potent emotional stimuli can “breakthrough” and override the effects of high perceptual load - a result that presents a challenge to load theory. All findings are discussed with reference to new challenges to load theory, particularly the “dilution” argument

Identifying key markers of visual short-term memory: How looking dynamics and physiology can inform our interpretation of change detection

Visual short-term memory (STM) is a foundational component of general cognitive ability that develops rapidly during the first year of life. Currently, it is unknow if visual STM performance in infancy reflects a similar memory mechanism used by adults. This is due to significant differences in the tasks used to measure visual STM performance in infant and adults. The current project has identified key behavioral and physiological indexes of visual STM performance in infants by utilizing data collected from adult participants in a similar task. In Experiment 1, adult visual dynamics were assessed during a change-detection task, and several key behaviors identified. In Experiment 2, these behaviors were subsequently observed in infants and adults while performing a similar change-detection task. Experiment 3 then applied infant-specific adaptations to an adult change-detection procedure, and again, found significant similar patterns of responding. Experiment 4 proposed a novel visual STM assessment technique, shedding light on the extent to which infant performance is uniquely influenced by incidental attention to individual array items. Results demonstrated that the order of fixation affected subsequent performance on a change-detection task. Combined, these results have identified an informative metric for understanding change detection in both infant and adult populations and have provided researchers with a novel method of measuring a cornerstone of cognitive development, visual STM. Taken together, results from these tasks demonstrate that visual dynamics such as saccade count, run count, average fixation duration, and changes in pupil size may be an ideal means of assessing visual STM ability in both infants and adults

Attentional Capture by Irrelevant Transients Leads to Perceptual Errors in a Competitive Change Detection Task

Theories on visual change detection imply that attention is a necessary but not sufficient prerequisite for aware perception. Misguidance of attention due to salient irrelevant distractors can therefore lead to severe deficits in change detection. The present study investigates the mechanisms behind such perceptual errors and their relation to error processing on higher cognitive levels. Participants had to detect a luminance change that occasionally occurred simultaneously with an irrelevant orientation change in the opposite hemi-field (conflict condition). By analyzing event-related potentials in the EEG separately in those error prone conflict trials for correct and erroneous change detection, we demonstrate that only correct change detection was associated with the allocation of attention to the relevant luminance change. Erroneous change detection was associated with an initial capture of attention toward the irrelevant orientation change in the N1 time window and a lack of subsequent target selection processes (N2pc). Errors were additionally accompanied by an increase of the fronto-central N2 and a kind of error negativity (Ne or ERN), which, however, peaked prior to the response. These results suggest that a strong perceptual conflict by salient distractors can disrupt the further processing of relevant information and thus affect its aware perception. Yet, it does not impair higher cognitive processes for conflict and error detection, indicating that these processes are independent from awareness

Change blindness and the primacy of object appearance

A large body of work suggests that the visual system is particularly sensitive to the appearance of new objects. This is based partly on evidence from visual search studies showing that onsets capture attention whereas many other types of visual event do not. Recently, however, the notion that object onset has a special status in visual attention has been challenged. For instance, an object that looms toward an observer has also been shown to capture attention. In two experiments, we investigated whether onset receives processing priority over looming. Observers performed a change detection task in which one of the display objects either loomed or receded, or a new object appeared. Results showed that looming objects were more resistant to change blindness than receding objects. Crucially, however, the appearance of a new object was less susceptible to change blindness than both looming and receding. We argue that the visual system is particularly sensitive to object onsets