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1 Watch this: One of the issues showing you this was that you had already seen a version in chapel what would we call this in research methods terms? In the original 1999 experiment at Harvard University 50% of participants did not notice the gorilla.

2 Inattentional Blindness Failure to notice an unexpected object in a scene when it remains in full view. By Ass Prof. Christopher Chabris

3 An Experiment in Change Blindness (Simons and Rensink, 2005) There is a change between the two slides presented they are separated (80ms) by a grey blank screen after every presentation. How long does it take you to notice the change?

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10 Change Blindness Results: Did you notice? 1. Engine missing under the wing 2. Background shading on US President Andrew Jackson changes colour. 3. The man standing on the left has pants that change colour. 4. The shadow on rear window of the blue car on the right changes. 5. The shadow of helicopter appears and disappears and reappears. 6. The bush to the left hand side of the sphinx disappears and reappears.

11 Perceptual Anomalies II Change Blindness is defined as a failure to detect that an object has moved or disappeared. (Eysenck) Refers to the failure of noticing large changes to scenes. (Grivas) Try the whodunit :

12 Change Blindness Levin and Simons investigated people s ability to detect continuity errors on film experimentally. They showed in the laboratory that large continuity errors (e.g. changes in clothing colour etc.) are not detected. Maybe it s because people are just not paying attention? ARE YOU???

13 Famous example: Luis Bunuel s That Obscure Object of Desire (1977) Same character played by two different actresses (Carole Bouquet and Angelina Molina), alternating unpredictably in different scenes. Typically not picked up by audiences!

14 Change Blindness How much of what we see do we really take in? Watch Video: Derren Brown Person swap. In Levin and Simons original door experiment only 50% people noticed the change. Change blindness only occurs if there is a gap between the two scenes, that acts as a disruption. The gap acts as a visual mask (occlusion event): the second scene must be compared to memory of first scene. Representation of first scene must be stored in visual short term memory (VSTM) that has a limited capacity.

15 Change Blindness extra info. Change detection requires a memory representation of the first scene. Few people have true photographic memories. Can only form an accurate VSTM memory representation of a small part of a complex scene. VSTM selection critically dependent on attention; that s why you need to be attending to the right part of the scene to detect the change. If you eliminate the gap between the scenes, we re much better at detecting the change. However if the change is made very gradual, then we re again poor. Why? We re very good at detecting transient changes in visual scenes. Yantis (1990) showed that transients capture attention. We detect them even if we re not attending to them. If you make the change very gradual there is no transient so it is not detected.

16 Change Blindness Attention Please! We believe we see an everyday scene in great detail and notice changes in it! BUT research suggests we only form fairly (NOT VERY) detailed visual representations of objects that are the focus of attention in the Long Term Memory LTM (Hollingwood & Henderson 2002). This limits our conscious experience and perceptions of the visual world.

17 Change Blindness Mindsight??? Mindsight (not proven) the feeling of seeing a change was investigated by Rensink in Using a flicker technique real world images alternated with one that had changed (like our experiment). t1 observers pressed a button when aware of the change. t2- pressed a button when visually experienced. 14/40 participants reported feeling a change.

18 Change Blindness Attention & Memory To perceive visual change we must have: Focused attention Visual memory Mental effort Without these visual information is overwritten and replaced & forgotten = inattentional amnesia.