Inattentional blindness or perceptual blindness (rarely called inattentive blindness) occurs when an individual fails to perceive an unexpected stimulus in plain sight, purely as a result of a lack of attention rather than any vision defects or deficits. When it becomes impossible to attend to all the stimuli in a given situation, a temporary "blindness" effect can occur, as individuals fail to see unexpected but often salient objects or stimuli.[1]
Inattentional Blindness
The term was chosen by Arien Mack and Irvin Rock in 1992 and was used as the title of their book of the same name, published by MIT Press in 1998,[2] in which they describe the discovery of the phenomenon and include a collection of procedures used in describing it.[3] A famous study that demonstrated inattentional blindness asked participants whether or not they noticed a person in a gorilla costume walking through the scene of a visual task they had been given.[1]
Research on inattentional blindness suggests that the phenomenon can occur in any individual, independent of cognitive deficits. However, recent evidence shows that patients with ADHD (Attention deficit hyperactivity disorder) performed better attentionally when engaging in inattentional blindness tasks than control patients did,[4] suggesting that some mental disorders may decrease the effects of this phenomenon. Recent studies have also looked at age differences and inattentional blindness scores, and results show that the effect increases as humans age.[5][6][7] There is mixed evidence that consequential unexpected objects are noticed more: Some studies suggest that we can detect threatening unexpected stimuli more easily than nonthreatening ones,[8][9] but other studies suggest that this is not the case.[10][11][12] There is some evidence that objects associated with reward are noticed more.[12]
The following criteria are required to classify an event as an inattentional blindness episode: 1) the observer must fail to notice a visual object or event, 2) the object or event must be fully visible, 3) observers must be able to readily identify the object if they are consciously perceiving it,[3] and 4) the event must be unexpected and the failure to see the object or event must be due to the engagement of attention on other aspects of the visual scene and not due to aspects of the visual stimulus itself.[3] Individuals who experience inattentional blindness are usually unaware of this effect, which can play a subsequent role on behavior.
Inattentional blindness is related to but distinct from other failures of visual awareness such as change blindness, repetition blindness, visual masking, and attentional blink. The key aspect of inattentional blindness which makes it distinct from other failures in awareness rests on the fact that the undetected stimulus is unexpected.[18] It is the unexpected nature of said stimulus that differentiates inattentional blindness from failures of awareness such as attentional failures like the aforementioned attentional blink. It is critical to acknowledge that occurrences of inattentional blindness are attributed to the failure to consciously attend to an item in the visual field as opposed the absence of cognitive processing.
Cognitive capture or, cognitive tunneling, is an inattentional blindness phenomenon in which the observer is too focused on instrumentation, task at hand, internal thought, etc. and not on the present environment. For example, while driving, a driver focused on the speedometer and not on the road is suffering from cognitive capture.[a]
While early research on the topic was heavily focused on early selection, research since the late 1970s has been shifted mainly to the late selection theories. This change resulted primarily from a shift in paradigms used to study inattentional blindness which revealed new aspects of the phenomenon.[21] Today, late selection theories are generally accepted, and continue to be the focus of the majority of research concerning inattentional blindness.
The effects of perceptual load on the occurrence of inattentional blindness is demonstrated in a study by Fougnie and Marois. Here, participants were asked to complete a memory task involving either the simple maintenance of verbal stimuli, or the rearrangement of this material, a more cognitively demanding exercise. While subjects were completing the assigned task, an unexpected visual stimulus was presented. Results revealed that unexpected stimuli were more likely to be missed during manipulation of information than in the more simple rehearsal task.[27]
The theory of inattentional amnesia provides an alternative in the explanation of inattentional blindness in suggesting that the phenomenon does not stem from failures in capture of attention or in actual perception of stimuli, but instead from a failure in memory. The unnoticed stimuli in a visual scene are attended to and consciously perceived, but are rapidly forgotten rendering them impossible to report.[28] In essence, inattentional amnesia refers to the failure in creating a lasting explicit memory: by the time a subject is asked to recall seeing an item, their memory for the stimulus has vanished.[29]
The very phenomenon of inattentional blindness is defined by a lack of expectation for the unattended stimulus. Some researchers believe that it is not inattention that produces blindness, but in fact the aforementioned lack of expectation for the stimuli.[23] Proponents of this theory often state that classic methods for testing inattentional blindness are not manipulating attention per se, but instead the expectation for the presentation of a visual item.[31]
Studies investigating the effect of expectation on episodes of inattentional blindness have shown that once observers are made aware of the importance of the stimuli to be presented, for example stating that one will later be tested on it, the phenomenon essentially disappears.[2] While admitting to possible ambiguities in methodology, Mack, one of the foremost researchers in the field, holds strongly that inattentional blindness stems predominantly from a failure of attentional capture. She points out that if expectation does not mediate instances of very closely linked phenomena such as attentional blink and change blindness (whereby participants have difficulty identifying the changing object even when they are explicitly told to look for it), it is unlikely that inattentional blindness can be explained solely by a lack of expectation for stimulus presentation.[23]
The perceptual cycle framework has been used as another theoretical basis for inattentional blindness. The perceptual cycle framework describes attention capture and awareness capture as occurring at two different stages of processing. Attention capture occurs when there is a shift in attention due to the salience of a stimuli, and awareness capture refers to the conscious acknowledgement of stimuli. Attentional sets are important because it is composed of characteristics of stimuli an individual is processing. Inattentional blindness occurs when there is an interaction between an individual's attentional set and the salience of the unexpected stimulus. Recognizing the unexpected stimulus can occur when the characteristics of the unexpected stimulus resembles the characteristics of the perceived stimuli. The attentional set theory of inattentional blindness has implications for false memories and eyewitness testimony. The perceptual cycle framework offers four major implications about inattentional blindness 1) environmental cues aid in the detection of stimuli by providing orienting cues but is not enough to produce awareness, 2) perception requires effortful sustained attention, interpretation, and reinterpretation, 3) implicit memory may precede conscious perception, and 4) visual stimuli that is not expected, explored, or interpreted may not be perceived.[32]
To test for inattentional blindness, researchers ask participants to complete a primary task while an unexpected stimulus is presented. Afterwards, researchers ask participants if they saw anything unusual during the primary task. Arien Mack and Irvin Rock describe a series of experiments that demonstrated inattentional blindness in their 1998 book, Inattentional Blindness.
The basic Simons and Chabris study was reused on British television as a public safety advert designed to point out the potential dangers to cyclists caused by inattentional blindness in motorists. In the advert the gorilla is replaced by a moonwalking bear.[36]
Participants were significantly more likely to notice the fight when the experiment was done during the day as opposed to in the dark. Additionally, sightings of the fight were most likely to be reported in the low load condition (72%) than in either the medium load (56%), or high load conditions (42%).[41] These results exemplify a real world occurrence of inattentional blindness, and provide evidence that officer Conley could indeed have missed the fight because his attention was focused elsewhere. Moreover, these results add to the body of knowledge suggesting that as perceptual load increases, less resources remain to process items not explicitly focused on, and in turn episodes of inattentional blindness become more frequent.
Another experiment was conducted by Steven Most, along with Daniel Simons, Christopher Chabris and Brian Scholl. Instead of a basketball game, they used stimuli presented by computer displays. In this experiment objects moved randomly on a computer screen. Participants were instructed to attend to the black objects and ignore the white, or vice versa. After several trials, a red cross unexpectedly appeared and traveled across the display, remaining on the computer screen for five seconds. The results of the experiment showed that even though the cross was distinctive from the black and white objects both in color and shape, about a third of participants missed it. They had found that people may be attentionally tuned to certain perceptual dimensions, such as brightness or shape. Inattentional blindness is most likely to occur if the unexpected stimuli presented resembles the environment.[42]
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