6. Attention & Perception copy.docx

CRITICAL READING: CORNELL NOTES Attention & Perception Name: Date: 10 August 2023 Section: Lecture 6 Period: Questions/Main Ideas/Vocabulary Notes/Answers/Definitions/Examples/Sentences Visual Processing Light is emitted or reflected from something in our environment. Light passes...

CRITICAL READING: CORNELL NOTES Attention & Perception Name: Date: 10 August 2023 Section: Lecture 6 Period: Questions/Main Ideas/Vocabulary Notes/Answers/Definitions/Examples/Sentences Visual Processing Light is emitted or reflected from something in our environment. Light passes through the eye lens to the retina. Photoreceptors in the retina are stimulated. Retinal ganglion cells are activated by light in their receptive fields. Action potentials are sent down the optic nerve to the LGN. The LGN transmits these signals to the primary visual cortex (V1). V1 projects into higher cortical areas for further processing. And we experience the world around us, exactly as it is. Change Blindness – Simons & Levin (1998) Only 50% of participants realised that the person they were helping changed. Even though they: Wore different clothes. Differed in height (~5cm). Had different voices. Inattentional Blindness Simons and Chabris (1999): Across 192 observers, 54% failed to notice the unexpected event. Task difficulty: Easy task = 64% noticed. Difficult task = 45% noticed. Beanland and Pammer (2010): Eye movements don’t predict IB. Noticers and non-noticers were equally likely to look at the unexpected event. Attention Your brain doesn’t process everything in your environment. Physiological constraints. Energy consumption. Processing constraints: There is far too much information in the environment. Attention is a mechanism to filter large amounts of information in order to aid our perception and action. By enhancing selected inputs. Or by suppressing irrelevant inputs. Neural Evidence of Attention Single cell recording: Rhesus monkey. Oriented line stimuli were presented onscreen, to attended and unattended locations. When presented at the same location in the receptive field, the same stimulus caused a larger response when attended than unattended. Ensemble Coding Humans can accurately identify scenes that have been presented for < 100ms. But a single saccade takes ~300ms. Our environment often contains redundant information, Blades of grass. Gist representations: Summary statistics. Set Representation Circle size: Sets of 4, 8, 12 and 16 circles presented for 500ms. Participants were very accurate when asked whether the test circle was smaller or larger than the set mean. But were at chance when asked to decide whether an individual circle was present in the set. Suggests rapid encoding of summary statistics of the set rather than individual items. Also seen for other attributes like orientation, speed, colour, brightness. Spatial Attention Metaphorically thought of as a spotlight that is developed to a particular region of space. Current models include the Zoom-lens. Over attention: The observer moves their eyes to the attended location. Covert attention: The observer deploys their attention to a location without moving their eyes. Covert attention can precede eye movements and overt attention. Depending on the task, attention might result in faster detection of a stimulus (reduced response time), or increased accuracy of detections. Posner Cueing Task Valid or invalid cues. CTOA: Cue target onset asynchrony. CTOA < 200ms Valid cue improves detection. CTOA > 200ms Valid cue inhibits detection. “Inhibition of return”. IOR begins about 250ms after onset. Top-Down vs Bottom Up Top down: You deliberately focus your attention on a particular stimulus or feature that is relevant to your processing goals. Bottom up: You attention is captured by the properties of the stimulus. Salience. Relative: A red shape will be highly salient is surrounded by blue shapes, but less so if surrounded by other red shapes. Attention capture: Testing conflict between top-down goals and salient bottom-up features. Gaze Cueing Valid eye gaze cues improve target detection, even when participants know the cues are only valid on 50% of trials. Eye gaze captures attention. Faces are often salient. Attentional Blink There is a significant, temporary decrease in the probability of detecting a second target after identifying the first. Lag of 200 – 500ms. Patient P.S. Step 1: Individually shown each card, asked to describe the drawing. “A house”. Step 2: Show both cards vertically. Asked whether they’re the same, and whether anything was wrong. “Same”, “No”. Step 3: Vertical presentation. Asked which house she would prefer to live in. “They are the same”. But when asked to choose anyway, Patient PS chose the house that wasn’t on fire 9 out of 11 times. Step 4: A house with fire was presented. PS immediately noticed the flames. Hemispatial Neglect Often cause by stroke in the right parietal lobe. An inability to orient or respond to visual stimuli in the contralesional visual field. Despite normal vision/motor function. Impaired visuospatial attention. Line cancellation task (a). Line bisection task (b). Treatments of Hemispatial Neglect Prismatic adaptation. Rehabilitation. Lateralisation of Visuospatial Attention Cerebral asymmetries: The left and right hemispheres of the brain have different specialisations. Left = language. Right hemisphere tends to be dominant for visuospatial processing. Hemispatial neglect is much more common after RH strokes. Imaging studies show that the RH posterior parietal lobe is implicated in the deployment of visuospatial attention. Ventral stream of visual processing. Pseudoneglect The tendency of healthy people to preferentially attend to the left side of space. A much smaller bias than hemispatial neglect. Bowers and Heilman: Control participants show a tendency to bisect lines to the left of centre. Jewell and McCourt: Pseudoneglect persists for pre-bisected lines, showing it isn’t a motor bias. A small effect of handedness, but both left and right handed individuals show the effect. McGeorge et. al: Representational pseudoneglect – participants recall more items from the left in memory. Pseudoneglect is apparent in the way we navigate our environment. Visual Search Feature search: The target is identifiable by a single feature (shape, orientation, size). Conjunction search: The target is defined by two or more features that make it unique (shape and colour). Parallel vs serial search. Feature integration theory: Pre-attentive vs attentive. Influential, but not quite so simple. Real World Visual Search Tasks Baggage screening. Medical imagery. Vigilance Decrement A decline in signal detection rate over the course of a sustained attention task. What Causes Vigilance Decrement? Shifting criterion (response threshold): Over time, participants increase the amount of evidence they require before reporting a signal (a double movement) – particularly when the signal is rare. Decline in sensitivity: As the task progresses, participants become less able to distinguish between signal and noise trials. Attentional lapses: Participants begin to mind wander as the task progresses and miss signal trials as a result. Recent research suggest that all three factors contribute: But that a change in response threshold and attentional lapses are mostly responsible.