‘Looking but not seeing’ an exploration of visual attention.

This essay will explore the concepts of ‘inattentional’ and ‘change’ blindness to explain how someone can fail to see stimuli that they are looking directly at. The main focus is on two famous experiments; "Gorillas in our midst: sustained inattentional blindness for dynamic events" by Simons and Chabris, (1999) which will be used to explain inattentional blindness and “Failure to detect changes to people during real-world interaction” by Simons and Levin (1998) which will be used to explain ‘change blindness’. However, the starting point for this discussion is attentional selection.

Active attentional selection occurs over space and time. The ‘spotlight’ has become the favoured metaphor for spatial attention because it captures some of the characteristics of attention - the feeling that attention can be used like a beam of light, to illuminate what is hidden. Cueing experiments have been an important tool for understanding spatial attention as a spotlight (Chun and Wolfe, 2001). In a cueing experiment, subjects are required to respond as quickly as possible to the onset of a light or other simple visual stimulus. This target stimulus is preceded by a “cue” whose function is to draw attention to the occurrence of a target in space. As a general rule, cues facilitate detection of and response to stimuli presented at the cued location. Posner consequently described attention as a "spotlight that enhances the efficiency of the detection of events within its beam" (Posner, 1980, p. 172).

The attentional spotlight theory is not the only metaphor used to describe visual attention. Eriksen and St. James (1986) proposed the zoom-lens metaphor. Rather than a beam of attention of a set size, they argued that we zoom in and out depending on the task. Like many metaphors, though, it is unwise to take them too literally. Subsequent findings examining the details have questioned several aspects of these theories raising two main objections to both: First, some studies suggest that attention can be split between two locations which has difficulty fitting with the idea of a single attentional 'beam' or 'lens' (Pylyshyn and Storm,1988). Second, research has shown that we can actually process visual stimuli outside the spotlight/zoom-lens quite thoroughly. McGlinchey-Berroth et al. (1993) revealed that patients with hemispheric neglect have been found to process visual information presented to their 'neglected' side.

Although there are problems with the attentional spotlight and zoom-lens as metaphors, they still provide a useful insight into how our attention can move independently of the eyes. The evidence also scientifically confirms the everyday experience of fixing the gaze and still being able to 'look around'. (Matlin, 2005)
Accordingly, when attention is not focused onto items in a scene they can go unnoticed. Therefore, Inattentional Blindness is the failure to see unattended items in a scene; literally ‘looking but not seeing’ (Mack and Rock, 1998). The scan path of the eye is therefore very strongly affected by visual attention. There are two general processes, called ‘bottom-up’ and ‘top-down‘, which determine where humans locate their visual attention (Braisby and Gellatly, 2005). The bottom-up process is entirely stimulus driven, for example, a candle burning in the dark or a pink taxi in a fleet of black cabs. In all these instances, the visual stimulus captures attention automatically without conscious choice. The top-down process, on the other hand, is directed by a voluntary control process which focuses attention on one or more objects which are relevant to the observer’s aim. Such aims may include looking for a street sign or counting the number of passes a team makes. In these scenarios, the conspicuous objects in a scene that would normally attract the viewer’s attention may be ignored if they are irrelevant to the task at hand. This is called ‘Inattentional Blindness‘. Recent psychological investigations have revealed that over half of people failed to detect fairly obvious elements of the environment when instructed to attend to a specific task. It has been discovered that most individuals (55%) fail to detect a man in a gorilla suit pass through a group of people passing a basketball when asked to count the number of times the ball is passed between the players (Simons and Chabris, 1999). Interestingly, in this experiment the ‘Gorilla’ walks in front of the ball on a couple of occasions crossing through the ‘spotlight’ and yet the majority of participants are blind to his existence despite stopping in the middle of the players and distinctively beating his chest. Inattentional blindness is a clear example of ‘looking but not seeing’. The next phenomenon that will be discussed is ‘change blindness’ which will show that even when someone’s attention is engaged they can fail to see an obvious change.

Simons and Levin (1998) approached pedestrians engaging them in conversation before changing the identity of the experimenter/conversationalist during the conversation. To make the change, they had two "workers" carry a door between the subject and experimenter. The results show that fifty percent of subjects failed to notice the change to a new person. The change blindness demonstration is interesting because, unlike inattentional blindness there is no question that observers have attended to the scene and to the objects in the scene. Nevertheless, considerable changes in the scene are missed. The changes are seen when the observer's attention remains with an object while it changes. Prior attention to the object is usually not enough, suggesting that the post-attentive visual representation is relatively vague.






















References.

Mack, A. and Rock, I (1998) Inattentional Blindness, Massachusetts Institute of Technology Press.

James, W. (1890) Principles of Psychology, New York:Holt.

Simons, D. J.; Chabris, C. F. (1999). "Gorillas in our midst: sustained inattentional blindness for dynamic events". Perception 28: 1059-1074.

Chun, M. M., Wolfe, J. M. 2001. Visual attention. E. Bruce Goldstein, ed. Blackwell Handbook of Perception. Blackwell Publishers, Oxford, U.K. pp272-310

Posner, M. I. (1980). Orienting of attention. Quarterly Journal of Experimental Psychology, 32, pp3-25.

Pylyshyn, Z., & Storm, R. W. (1988). Tracking multiple independent
targets:evidence for a parallel tracking mechanism. Spatial Vision, 3, 179-197.

McGlinchey-Berroth, R., Milberg, W.P., Verfaellie, M., Alexander,
M., & Kilduff, P.T. (1993). Semantic processing in the
neglected visual field: Evidence from a lexical decision task.
Cognitive Neuropsychology, 10, 79–108.

Simons, D.J., & Levin D.T. (1998). Failure to detect changes to people during real-world interaction. Psychonomic Bulletin and Review, 4(5), 644-649.

Braisby, N., Gellatly, A. (2005) Cognitive Psychology. New York: Oxford University Press Inc.

Matlin, M.W. (2005) Cognition. USA: John Wiley & Sons. (6th ed.)

Cater, K., Chalmers, A., Ledda, P.(2002) Selective Quality Rendering by Exploiting Human Inattentional Blindness: Looking but not Seeing. Symposium on Virtual Reality Software and Technology. Nov, pp. 17–24.