Change Blindness

Background

Change Blindness refers to people's consistent problems noticing changes to the location and identity of objects in visual scenes if brief interruptions occur. Ronald Rensink and colleagues coined the term in 1997 in their classic paper on the "flicker paradigm," where two alternating versions of an image are separated by a brief blank screen. For example, in a typical flicker task, a detail like a vendor's pants might change from red to blue, yet participants often stay unaware of the changes occurring right in front of their eyes. Daniel Simons and Daniel Levin demonstrated the phenomenon in a real-life setting in 1998, where an experimenter asking a pedestrian for directions was momentarily blocked by a passing door carried by construction workers. During the brief interruption, the experimenter swapped places with a completely different person. Remarkably, over half of the participants didn't notice they were talking to someone new.

Rensink (2000) argued that a change can be detected only if the object is the focus of attention when the change occurs. According to him, without focal attention, object representations exist in a kind of "proto-object" state; they are continually formed in parallel, are incoherent, and are easily replaced by new visual stimuli when they appear. With focused attention, however, these mental object representations gain coherence by being anchored in time and space, and thus have a higher chance of being recalled should they suddenly change. Melissa Beck and Daniel Levin (2003) propose that attention may indeed result in coherent object representations that can support change detection, but that change detection alone does not guarantee accurate recognition of the changed object. Thus, noticing that something changed may be a different cognitive mechanism than remembering what it used to look like.

Task Procedure

The Millisecond Change Blindness Task is based on the published procedure by Beck & Levin (2003). The test runs 56 trial sequences with 3 to 16 array objects with each level being repeated four times. All array objects are distributed randomly across a 4x4 matrix. Each trial sequence consists of a 'pre-change array', a 'post-change array' and two 4FC recognition tasks. The pre-change array presents the initial image scene with the specified number of array items. Items are selected randomly. The pre-change scene is presented for 2seconds and then erased by a blank screen for 350ms. The post-array scene presents almost the same scene but has swapped one item for a new one. It is also shifted slightly to the left or right. Like the pre-change array, it is presented for 2s and then replaced by a blank screen for 350ms. The first 4FC recognition task asks participants to select the pre-change object that was changed from the pre to the post scene. The second 4FC recognition task asks participants to select the post-change object that was present in the post-scene but not in the pre-scene. Both recognition tasks provide four choices. The four objects consist of the correct solution, a foil object (an array item that was present in both scenes), and two scene-unrelated items. The order of the four objects is determined randomly.

By default, the tasks starts participants with an optional practice session. The practice session runs 10 practice trials with scenes that depict 4 objects and provides error feedback.

What it Measures

Change Blindness Tasks measure the limits of human visual attention, perception, and working memory

Psychological domains

• Attention and Perception: Impact of attention on our perceptual system
• Working Memory: The capacity and volatility of visual short-term memory (VSTM).

Main Performance Metrics

• Hits: Number of pre/post recognition hits, separately for each level of n
• False Alarms: Number of pre/post foil selections, separately for each level of n
• Difference Scores: Difference scores of hits and false alarms for pre/post scenes, separately for each level of n

Psychiatric Conditions

Change Blindness tasks have been used with the following clinical populations

• Mild Cognitive Impairment (MCI)
• Autism Spectrum Disorder (ASD)
• Attention Deficit Hyperactivity Disorder (ADHD)
• Stroke
• Schizophrenia

References

Search Google Scholar for peer-reviewed, published research using the Inquisit Change Blindness.

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Phillips, W.A. (1974). On the distinction between sensory storage and short-term visual memory. Perception and Psychophysics , 16, 283–290.

Pashler, H. (1988). Familiarity and visual change detection. Perception and Psychophysics, 44(4), 369–378.

Simons, D.J. (2000) Current approaches to change blindness. Visual Cognition, 7, 1-15.

Beck, M.R. & Levin, D.T (2003). The role of representational volatility in recognizing pre- and postchange objects. Perception & Psychophysics, 65, 458-468.

Beck, M.R., Levin, D.T., Angelone, B. (2007). Change blindness blindness: Beliefs about the roles of intention and scene complexity in change detection, Consciousness and Cognition, 16, 31-51.

Koustanaï, A, van Elslande, P., Bastien, C. (2012). Use of change blindness to measure different abilities to detect relevant changes in natural driving scenes, Transportation Research Part F: Traffic Psychology and Behaviour, 15 (3), 233-242.