Inattentional blindness: looking without seeing

Surprising as it may seem, research shows that we rarely see what we are looking at unless our attention is directed to it. This phenomenon can have serious life-and-death consequences. Although the inextricable link between perceiving and attending was noted long ago by Aristotle, this phenomenon, now called inattentional blindness (IB), only recently has been named and carefully studied. Among the many questions that have been raised about IB are questions about the fate of the clearly visible, yet unseen stimuli, whether any stimuli reliably capture attention, and, if so, what they have in common. Finally, is IB an instance of rapid forgetting, or is it a failure to perceive?     

Inattentional blindness for negative relationships in human causal learning

The present study focuses on the effect of selective attention on causal learning. Three effects of the level of attention to predictive symptoms in positive and negative contingency learning tasks are reported. First, participants accurately detected a positive relationship between an incidental cue and a contingent outcome, although judgements were slightly lower than those for the attended cue. Second, participants were unable to detect negative relationships between incidental cues and outcomes, which suggests a major role of selective attention in this type of learning. Third, participants retrieved the frequency of each trial type more accurately in the attended conditions than in the incidental conditions. These findings show how attention guides and constrains human causal learning and reveal an inattentional blindness effect for negative contingency learning.     

Inattentional blindness for ignored words: Comparison of explicit and implicit memory tasks

Inattentional blindness is described as the failure to perceive a supra-threshold stimulus when attention is directed away from that stimulus. Based on performance on an explicit recognition memory test and concurrent functional imaging data Rees, Russell, Frith, and Driver [Rees, G., Russell, C., Frith, C. D., & Driver, J. (1999). Inattentional blindness versus inattentional amnesia for fixated but ignored words. Science, 286, 2504–2507] reported inattentional blindness for word stimuli that were fixated but ignored. The present study examined both explicit and implicit memory for fixated but ignored words using a selective-attention task in which overlapping picture/word stimuli were presented at fixation. No explicit awareness of the unattended words was apparent on a recognition memory test. Analysis of an implicit memory task, however, indicated that unattended words were perceived at a perceptual level. Thus, the selective-attention task did not result in perfect filtering as suggested by Rees et al. While there was no evidence of conscious perception, subjects were not blind to the implicit perceptual properties of fixated but ignored words.     

Inattentional blindness as a function of proximity to the focus of attention.

The effect of the distance between the center of the focus of attention and an unexpected stimulus on detection was examined in two experiments with the use of the inattentional-blindness paradigm [Mack and Rock, 1998 Inattentional Blindness (Cambridge, MA: MIT Press)]. In experiment 1, the closer a stimulus was to the center of attention, the more likely it was to be detected. Experiment 2 replicated this finding and controlled for retinal eccentricity. These results suggest that low-level stimulus characteristics (e.g. location) may play an important role in the detection of unexpected stimuli. The data are consistent with previous research on the spatial aspects of attention demonstrating that the distance to the focus of attention is a critical variable. This study demonstrates that the effect of distance is similar under conditions of inattention. Theories put forward to explain inattentional blindness should include 'early' attentional factors, as well as factors resulting from later stages of processing.     

Fire drill: Inattentional blindness and amnesia for the location of fire extinguishers

Fire extinguishers can save lives and are placed in locations that make them easily accessible and in plain view in case of an emergency. However, despite having viewed these bright red objects many times, people may be unaware of their precise locations or even of the fact that they have seen them so often in their workplace environment. We tested the ability of occupants of an office building to recall the location of the nearest fire extinguisher, as well as other objects (e.g., clock, drinking fountain). Despite years of exposure to it, a majority failed to remember the location of the nearest fire extinguisher, although they were able to locate it relatively quickly when asked to search for it. The results support an important distinction between seeing and noticing objects and reveal a novel form of inattentional amnesia for salient objects. The study also created an important learning event via failed retrieval, which could be essential to survival.     

The dark side of visual awareness in sport: Inattentional blindness in a real-world basketball task

Most research in the field of decision making in sports has focused on the bright side of visual attention and has not taken the dark side of visual awareness into account. Understanding the costs of such inattention should be complementary to the study of how attention facilitates perception. In the present study, we provide evidence for the existence of inattentional blindness (IB) in a real-world basketball setting among adults (Experiment 1). In Experiment 2, we found that players with hardly any basketball experience were more likely to experience IB in a real-world basketball setting, as compared with experienced athletes. Improving the ecological validity of the setting by enhancing the perception-action coupling (Experiment 3) and increasing task difficulty (Experiment 4) did not appear to affect the occurrence of IB among experienced athletes. IB can be considered a limitation of the visual system, but it also highlights a critical aspect of visual processing, which allows us to remain focused on the important aspects of the world. But as is shown in the present experiments, it is possible to induce an attentional set—for example, by sport-specific instructions—that leads to players’ missing important game-relevant information.     

When you fail to see what you were told to look for: Inattentional blindness and task instructions

Inattentional blindness studies have shown that an unexpected object may go unnoticed if it does not share the property specified in the task instructions. Our aim was to demonstrate that observers develop an attentional set for a property not specified in the task instructions if it allows easier performance of the primary task. Three experiments were conducted using a dynamic selective-looking paradigm. Stimuli comprised four black squares and four white diamonds, so that shape and colour varied together. Task instructions specified shape but observers developed an attentional set for colour, because we made the black–white discrimination easier than the square–diamond discrimination. None of the observers instructed to count bounces by squares reported an unexpected white square, whereas two-thirds of observers instructed to count bounces by diamonds did report the white square. When attentional set departs from task instructions, you may fail to see what you were told to look for.     

Schedules using noxious stimuli. II: low intensity electric shock as a discriminative stimulus

The presence or absence of pulses of low intensity electric shock was used as a discriminative stimulus to control responding under fixed ratio reinforcement in the squirrel monkey. Initially brief periods of nonreinforcement were lengthened only when discriminative control was evident. Discriminative control was studied by (1) varying the duration of nonreinforcement periods; (2) reversing the stimulus conditions correlated with reinforcement and nonreinforcement periods; and (3) determining the minimum shock intensity necessary to maintain discriminative control. Stimulus control was not reliably affected by d-amphetamine, chlorpromazine, or morphine. The discriminative control by pulses of low intensity electric shock was similar to that by other discriminative stimuli, except that the control developed slowly and was better when the pulsing shock was correlated with reinforcement than when correlated with nonreinforcement.     

The influence of attention upon anticipatory arousal,habituation, and reactivity to a noxious stimulus

Forty subjects were assigned to four groups, an External-attending Group, an Internal-attending Group, a Control Group, and a Distracted Group. All groups were presented with six trials of a 0.5-sec 110-db white noise. A measure of heart rate deceleration verified the experimental manipulation of attention. During the anticipatory period, the Internal-attending Group exhibited the greatest and the Distracted Group exhibited the least reactivity among the four groups. The two specially attending groups exhibited greater galvanic skin-response conditioning during the anticipatory period than the other groups. There was no support for the hypothesis that heightened attention facilitates habituation. Two measures were differentially sensitive to direction of attention during the anticipatory period. The External-attending Group exhibited reliably greater anticipatory deceleration of heart rate than the Internal-attending Group, while the Internal-attending Group exhibited reliably more nonspecific electrodermal responses than the External-attending Group. This latter finding, along with other evidence, suggests that an inward direction of attention tends to exacerbate anticipatory anxiety as well as reactivity to the impact of a noxious stimulus.     

Repetition blindness: The effects of stimulus modality and spatial displacement

Repetition blindness (Kanwisher, 1986, 1987) is the failure to detect repetitions of words in lists presented in rapid serial visual presentation (RSVP). Two questions were investigated in the present study. First, if repetition blindness is not found with auditory presentation, it would support a specifically visual account of the effect. Second, if displacement of the two instances in visual space eliminates repetition blindness, it would suggest that repetition blindness is restricted to instances in which identical stimuli are distinguished soley by temporal differences. In Experiment 1, the subjects omitted second occurrences of repeated words in verbatim recall of rapid sentences presented visually (in RSVP), but not auditorily (using compressed speech), indicating that repetition blindness is a modality-specific phenomenon. In Experiments 2 and 3, repetition blindness was observed even when two occurrences of a written word were presented in different locations, showing that distinct locations do not guarantee token individuation. The results are discussed within a model that distinguishes between processes of type recognition and token individuation.     

Preceding stimulus awareness augments offset-evoked potentials: Evidence from motion-induced blindness

Event-related potentials (ERPs) were measured in response to the objective offset of a visual disk under two physically similar conditions: (1) visible conditions in which the target disk was well perceived and (2) invisible conditions in which participants reported to have not seen the target because of motion-induced blindness (Bonneh, Cooperman, & Sagi in Nature 411:798-801, 2001). Electrophysiological responses to the physical offset of the target disk were almost completely absent in the invisible conditions (Experiment 2). In the same conditions, the physical offset was almost completely invisible (Experiment 1). Results suggest an augmenting function of prior awareness of a stimulus for the offset-triggered ERP of that stimulus.     

Effects of multimodal presentation and stimulus familiarity on auditory and visual processing

Two experiments examined the effects of multimodal presentation and stimulus familiarity on auditory and visual processing. In Experiment 1, 10-month-olds were habituated to either an auditory stimulus, a visual stimulus, or an auditory-visual multimodal stimulus. Processing time was assessed during the habituation phase, and discrimination of auditory and visual stimuli was assessed during a subsequent testing phase. In Experiment 2, the familiarity of the auditory or visual stimulus was systematically manipulated by prefamiliarizing infants to either the auditory or visual stimulus prior to the experiment proper. With the exception of the prefamiliarized auditory condition in Experiment 2, infants in the multimodal conditions failed to increase looking when the visual component changed at test. This finding is noteworthy given that infants discriminated the same visual stimuli when presented unimodally, and there was no evidence that multimodal presentation attenuated auditory processing. Possible factors underlying these effects are discussed.     

Repetition blindness for novel objects

When visual stimuli (letters, words or pictures of objects) are presented sequentially at high rates (8–12 items/s), observers have difficulty in detecting and reporting both occurrences of a repeated item: This is repetition blindness. Two experiments investigated the effects of repetition of novel objects, and whether the representations bound to episodic memory tokens that yield repetition blindness are viewpoint dependent or whether they are object centred. Subjects were shown coloured drawings of simple three‐dimensional novel objects, and rate of presentation (Experiment 1) and rotation in depth (Experiment 2) were manipulated. Repetition blindness occurred only at the higher rate (105 ms/item), and was found even for stimuli differing in orientation. We conclude that object‐centred representations are bound to episodic memory tokens, and that these are constructed prior to object recognition operating on novel as well as known objects. These results are contrasted with those found with written materials, and implications for explanations of repetition blindness are considered.