Summary Sensation and Perception Chapter 6 - 10 PDF

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Chapter 6 Notes: Visual AttentionScanning a Scene  Visual Scanning allows the cone rich fovea to be exposed to the highest level of detail. This movement is also called a Saccadic eye movement between Fixations  Overt/Covert Attention refers to looking directly (or not) at the object. What directs...

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PSYC 2018

1 Chapter 6 Notes: Visual Attention

Scanning a Scene  Visual Scanning allows the cone rich fovea to be exposed to the highest level of detail. This movement is also called a Saccadic eye movement between Fixations  Overt/Covert Attention refers to looking directly (or not) at the object. What directs this attention?  Stimulus salience = physical properties (colour, movement, orientation ect.) which make the object ‘conspicuous’. o This can cause an involuntary shift of attention called an attentional capture (Anderson et al, 2011) o Combining all the differences a way of analysing this saliency, is by creating a Saliency Map, where highly salient objects are shown as bright.  Cognitive Factors o This has a very large variance between people. This top-down process is associated with scene schemas (expectations)  E.g. if a printer is placed on a stove instead of a pot, people will pay more attention to it, as it disobeys their schema (Vo and Henderson 2009)  Hiroyuki Shinoda (2001) found 45% of observers’ fixations on stop signs happened at traffic intersections, with many missing signs placed in between – when driving through a CG environment - This is due to the Schema and Task Demands  Task Demands o ‘Just in time’ strategy-eye movements occur just before the information is needed. o Scene Statistics of dynamic events are seen in Jovancevic-Misic and Hayhoe (2008) when participants walked around an elliptical pathway and were told to avoid pedestrians. The ‘rogue’ or ‘Risky’ peds were looked at over 4x more than the ‘safe’. What happens when we attend?  Attention speeds o Posner et al (1978) used precueing to find that cued stimuli were reacted to faster than when the cue was invalid.(see right)

PSYC 2018 o We also attend more to objects we recognise/know – similar to cognitive factors. o Same-object advantage allows for an enhancement of the entire object of attention, even when only a section of it is focused on.  Attention Influencing Appearance o Carrasco et al (2004) experiment provided evidence for “clear and vivid” effect on attention. A ‘fixation dot’ was shown on a screen, with a flashed cue dot – followed by the slanted stimuli. The task asked the individuals to identify which of the slanted gratings was brighter. If the cue was on the one side, when the stimuli were of equal brightness, then they would label the cueside as brighter.  Attention influencing physiology o Attention to different stimuli provided different responses in O’Craven et al’s (1999) experiment finding faces FFA, houses PPA and movement MT/MST o Covert attention also causes a change in brain activity. o Womelsdorf et al (2006) found a monkey’s shift in attention can shift the receptive field. This movement allows for the neural processing to concentrate on what is important to the perceiver. What happens when we don’t attend?  Inattentional Blindness – not seeing/perceiving what you don’t attend o Cartwright-Finch and Lavie presented flashing cross stimuli and participants were asked to say which arm was which colour. On the 6th trial a square was added. Only 2/20 participants reported it. o Simons and Chabris (1999) basketball invisible gorilla experiment. 46% didn’t report seeing the gorilla. Although is this a strong enough result?  Change detection – resulting in Change Blindness o Relevant to continuity errors in film.  Is attention Necessary? o Possibly not as people can perceive the gist of scene after ¼ second. o Fei Fei Li et al (2002) tested using a dual task procedure, with one in central and one in the periphery. Found 90% accuracy in a peripheral picture task, while sill remaining correct in the central task – however this dropped to 50% on the peripheral coloureddisc task. This also suggests that scenes are easier to perceive.  Cohen et al (2011) performed another study to test this further, creating a more distracting central task. He found that the picture identification dropped to 63%, although this is still above chance. Distracting Effect of Task-Irrelevant Stimuli  Distraction o Easy tasks are highly affected, hard tasks are affected less.

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PSYC 2018 Lavie’s load theory of attention involving perceptual capacity and load o Capacity is the idea of a maximum amount of data for a task. o Load is the amount of that capacity needed to carry out the task.  Low-Load tasks are easy/rehearsed/practiced ones as opposed to High-Load Attention effecting coherence of perception  Binding is when all features are combined to create the perception (colour, shape, motion etc.) o The Binding Problem asks how when shape in the IT cortex, movement in the M temporal cortex and colour in other areas fire at the same time to produce a coherent percept.  Feature Integration Theory – Presented by Anne Teisman o Happens in steps 1. Preattentive stage where the objects are analysed and separates into features, which therefore are independent at this stage. a. Evidence for this is from Treisman and Schmidt (1982) who flashed complex stimuli (an array of shapes and colours) for 1/5 second. On 18% of trials participants confused features. These are called Illusionary Conjunctions. 2. Focused Attention Stage where features are combined to make a coherent view. Here attention plays an important role. a. Support from R.M. case study, who had parietal lobe damage (Balint’s syndrome) causing an inability to focus attention on individual objects. They formed many illusory conjunctions, even when given 10 seconds to look at the stimulus. Supporting this role of attention, and the model as a whole. 3. Bottom-up processing is the main approach in this theory, however top-down will have an effect. Triesman and Schmidt (1982) tested with shapes, then told participants that they’d see a ‘carrot, lake and tyre’, for which fewer illusory conjunctions occurred. Although is this due to expectation, not perception?  Visual Search o Feature search (one element) or Conjunction search (Many elements)  Again, evidence from R.M. which showed an ability to complete feature searches, but not conjunction searches. This is because a conjunction search requires attention at a location, while feature does not. Attention in Autism  Attention is crucial in social interaction – as well as perception.  People with Autism have difficulty with eye contact.  Eye movement is also more sporadic and random in those with autism. Although it is not clear why. 

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PSYC 2018 o One explanation for this, regarding faces, is due to autistics not being able to recognise faces as a whole, only as parts. o Pelphrey et al (2005) measured activity in the STS (superior temporal sulcus). Non-autistic individuals’ STS was activated more when eye movement was incongruent (not representative to the subject looked at) while autistics had equal activation.  This is explained as autistic individuals would not expect the person to look at the checkerboard – due to a lack of pairing. Developmental aspect  Many attentional processes don’t occur util after 3 months, continuing to develop until adolescence.  How does this effect perceptual completion (the perception of objects which extend behind occluding ones. o To test Habituation (repeated viewing) which finds infants will always look at a more novel object.  Habituation occurs when individuals pay less attention because the object is familiar while dishabituation occurs when a new object is placed when the habituated is expected. o Kellman and Spelke (1983) bar behind block test, 4 month old infants looked for longer if the bar was in fact two shorter bars – instead of the anticipated single bar. (as it goes against their inference)  Experiment repeated by Slated et al (1990) with newborns, finding they looked for longer at the single rod, therefore making no assumption.  But when does this ability develop? Johnson and Aslin (1995) repeated the experiment at 2 months, finding similar results to 4 months. Meaning this is a process which happens very early, but is strongly connected to detecting motion.  However further research Johnson et al (2008) suggests that motion isn’t the variable, as the correlation between an infant perceiving motion and their score in the task isn’t proportional. Suggesting it is more closely linked to scanning patterns of the eye and habituation.

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PSYC 2018

1 Chapter 7: Taking Action

The Ecological Approach to perception (Groundwork by J. J. Gibson)  Key Ideas o Optic Flow provides information of movement in relation to you and has two characteristics. 1. Optic Flow is more rapid near the observer, the change in this from far to near is called the gradient of flow – and this is what tells the observer of their speed. 2. There is no flow at the destination towards which the observer is moving, this point is called the focus of expansion (FOE) o Invariant Information is information which remains constant in movement. Such as the actual shape and size of objects, or the FOE point o Self-produced information is the information produced by movement. It can be seen that this helps to guide gymnasts, as experts (not novices) perform better when their eyes are open (Bardy and Laurent 1998)  Senses don’t work in isolation o Consider standing up, it uses the ear canal, receptors in joints/muscles and vision.  Lee and Aronson (1974) put 13-16 month toddlers into a room where the walls could swing, while the floor was stationary. They found that when the wall moved towards them the flow pattern would represent movement forwards, and they would therefore compensate by leaning back. Likewise with away, but to the extent of falling! The movement affected 82%! A similar trend was found in adults.  (see right) Navigating through the environment  Is Optic Flow used? o The MST (medial superior temporal area) is seen to respond to flow patterns. o Britten and van Wezel (2002) showed a monkey a left moving stimulus and recorded their response, when also stimulating the

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MST the monkeys response went from 60 to 80%  This supports the role of neurons in Optic Flow and therefore its usefulness. o Land and Lee (1994) performed an experiment on drivers finding that they rarely looked towards the FOE, instead favouring the road in front of the car (when straight) or the tangent to the corner (when turning). This suggests there is more than just optic flow working. o Walking: Visual direction strategy suggests the drifting of the target in vision provides the information that one is going off course, which may also be used in other modes of movement.  Loomis et al (1997) tested a similar thing with participants’ eyes closed, while they still managed to walk towards and stop nearby a target.  Wayfinding o The role of Landmarks was studied by Hamid et al (2010), by running participants through a virtual maze with various landmarks at either decision or non-decision locations. Those at decision locations were looked at for longer, and had a greater impairing effect when removed.  Other studies have found that these recognised points also create more brain activity in the parahippocampal gyrus.  Janzen and van Turennout (2004) asked participants to familiarise themselves with a museum layout from a video. They measured activity in an fMRI finding both remembered and forgotten decision point stimuli (landmarks) triggered greater activity. They concluded that this meant the brain automatically distinguishes landmarks for navigation. o Brain Damage’s effect  Retrosplenial Cortex damage causes difficulty in recognising direction even when the individual can perceive landmarks they are familiar with, and remember the layout of a room.  Hippocampus Damage – Patient T.T., a taxi driver, was damaged in this area and could direct themselves through main roads but not when he travelled onto a side road. Acting on Objects  Affordances: Essentially what objects are used for (Also proposed by Gibson) o This suggests another layer to our perception of an object; how we can use it. o Patient M.P. had damage to temporal lobe, impairing ability to name objects. He was asked to recognise, out of 10, which object was either the named object or the one that did a said task. He was more accurate and rapid when given the function. Suggesting he was using his affordances to identify the object.  However this experiment didn’t correspond directly to action only identification

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Physiology of reaching and grasping. o Dorsal (where/how) and Ventral (What) pathways (Refer back to D.F., mailbox task chapter 4)  The process of grasping and picking up continually utilises both pathways. o Parietal Reach Region (PRR), is at the end of the dorsal pathway contains neurons for grasping and reaching. However recent evidence suggests that this area is split and spread across the lobe, while areas near the PRR still responded.  Fattori et al (2010) monkey hand grip experiment. Stages 1) monkey observes fixation light 2) object is revealed momentarily 3) fixation light changes colour signalling them to grasp.  This found different neurons responded to different grips, but remember it was in the dark so it relates to action not perception.  In a follow up (Fattori et al 2012) they found neurons which fired to both the action and perceiving of a grip. Fattori called these visuomotor grip cells  Avoiding other Objects o Obstacle avoidance is also controlled by the Parietal Region  Schindler et al (2004) demonstrated this with patients who had damaged parietal lobes (a specific type causing optic ataxia) They were asked to put their hands between two cylinders and touch a strip. Ataxia patients didn’t alter their movement no matter the placement of the cylinders, while non-ataxia participants did.  Schindler suggests this means that the dorsal stream not only provides guidance to where we go, but guidance away from obstacles. Observing others’ actions  Mirror Neurons exist in the premotor cortex, named as they mirror what is seen. o Rizzolatii et al (2006 see diagram) observed that, in monkeys, these cells fired both when they picked up food and when the experimenter did. Therefore firing for both doing, and observing the action. However they do not fire as strongly.  But are these just responding to motion? Arguably no, as if the experimenter picked up the food with, say, pliers the activation was much less. 

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o Further experimentation found audiovisual mirror neurons, which respond to sounds associated with the certain action.  This was found by Kohler et al (2002) who also found that the neuron fires for 1) Seeing and Hearing 2) Seeing 3) Hearing 4) Doing the action of breaking a peanut. This suggests that it doesn’t respond to the action but actually what is happening.  Prediction of actions o Icoboni et al (2005) tested actions while altering the surroundings to suggest different intentions. They found that the action alone yielded the lowest brain response, while coupled with the intended action of drinking or cleaning yielded higher (drinking being highest)  It is suggested that these mirror neurons also help to understand: facial expressions, gestures in relation to speech, meanings of sentences and differences between people (therefore social drives)  However as with any discovery, this is likely to be later disproved. Action-Based Accounts of Perception  Approach: Vision is not primarily for creating perception, but to aid us in guiding out actions. Think evolutionary. The two step process of perception-action. o Similar approach from Mel Goodale (2011) “Many researchers now understand that brains evolved not to enable us to think (or perceive), but to enable us to move and interact with the world”  Question use of ‘understand’, this isn’t fact.  Alternative approaches arguing the opposite, “perception depends on action”, “action depends on perception” or even “people perceive their environment in terms of their ability to act on it”. o Perception affected by performance: sports experiments – Witt and Proffitt (2005) softball side, better=bigger. Witt and Sugovic (2010) Tennis, better= lower net. Witt and Dorsch (2009) football, scorers=wider goal.  Similar result when asking unfit people about the steepness of a hill, those more fit perceived it as less steep. Bhalla and Proffitt (1999)  But is this perception or conception (expectation) o Highlighting issue of measuring perception, we only receive their response, not their raw percept.

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PSYC 2018

1 Perception Chapter 8 Notes

Functions of Motion Perception  Fundamental link to survival o This provides attentional capture, relating to the ‘play dead’ or freezing of animals when they sense danger.  Optic Flow o The movement of the environment from an individuals perspective during movement – it provides them with information about direction and speed  Akinetopsia o The inability to perceive motion (motion blindness), makes it difficult to pour a drink or listen to a conversation (due to no mouth/lip reading) Studying Motion Perception  Real Motion is when something actually moves  Illusionary Motion is when there is no actual movement but it is perceived o Apparent Motion (a type of Illusionary motion) is seen by alternating stimuli dots, and is used in film (24fps). o Induced motion movement of larger objects, making a smaller object appear to be moving o Motion aftereffects – such as the waterfall illusion cause certain neurons to become ‘worn-out’ and produce false movement in the opposing direction.  Axel Larsen et al (2006) found areas in the brain activated by no, real and apparent motion. Finding the greatest stimulation on real motion.  Retinal image problem. The motion perceived does not directly reflect movement of stimuli across the retina, as if the head is turned motion appears on the retina yet is not perceived by the viewer

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Information in the Environment  Optic Array is the structure created by surfaces textures and contours of the environment – Optic flow occurs when this moves. o Local disturbance to the optic array occurs when something moves through it. o Global optic flow is when an entire environment shifts across the retina, signalling the movement of the eye, and the stationary nature of the environment. Retina/eye information  The Richardt Detector [see right] (Werner Reichardt 1969) was proposed as a neural explanation for motion perception, explaining this through neurons firing to movement in one direction. (See textbook p 182) o This process includes inhibition and excitation in turn, depending on the motion of the object. Therefore direction is deciphered by excitation or inhibition of firing. o However this explanation can only account for movement across receptors. (not eye movement)  Corollary Discharge Theory o This takes into account signals from the retina and the eye muscles with different types:  Image displacement signal (IDS) a simple movement across the FOV  Motor signal (MS) signal sent from the brain to eye muscles, inducing eye movement.  Corollary discharge Signal (CDS) is a copy of the MS (motor signal) which informs the brain of the eye movement. o These signals solve the problem suggesting that if one signal (IDS or CDS) is sent to the brain then motion is perceived but if both signals occur simultaneously no motion is perceived.  These signals are received in the Comparator which compares the incoming signals, however this is probably located around the brain in many parts o Behavioural Evidence for Corollary Discharge Theory  Afterimage not moving when eyes are moved (remains stationary to background) this cannot be due to motion across the retina, as it is in the same place. Therefore the CDS must be effecting the ‘movement’ of it.

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Pushing the eyelid causes movement in the eye muscles however when Stark and Bridgeman (1983) asked participants to focus on a single location when doing the activity the eye ...