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PSYB51H3 (314)
Lecture 7


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Matthias Niemeier

PSYB51 Lec 7 SAQ: what is the horopter? - Objects that have zero disparity - Images or objects projected on corresponding pieces of the retina - We turn our eyes toward something ex. when finger is moving closer to our faces - Like a 2D ring surface - All the points on that surface have zero disparity - Horopter is located wherever the eyes are focused on o If looking at our finger in front of us, the horopter is smaller o When looking at something far away, horopter is bigger Attention - Attention (selective) is a cognitive brain mechanism that lets one process different information and block out that which is irrelevant or distractive - Arousal: global state of the brain reflecting an overall level of responsiveness o Varies depending on how alert or aroused we are – can take in more or less information - Relationship between attention and arousal: inverted U o As arousal is increased, (ex. first waking up and taking one cup of coffee) can take in more information o When waking up and having 20 cups of coffee, try to attend to everything  Attention declines as arousal increases Why we need attention - Bottlenecks: having something that has a wide opening, then becomes narrow then becomes wide again o Ex. having a bottle  Everything has to pass through bottleneck  Limitations to how much can flow in and out o Impossible to process everything at the same time - Ex. where’s waldo games o Sensory bottleneck o Also bottlenecks based on motor outputs  Need to focus on one thing at a time Why can attention help us - How we benefit from selecting: - When paying attention to certain things, we are much faster at seeing changes in that area - If we want to select where we want to pay attention, we notice changes o Ex. loud noises, people moving, etc - We use criteria to notice what is important Classic measure of attention: how quickly you respond to something - Reaction times - Eye movements can reflect attention o OVERT shifts in attention  See it in behaviour Posner’s Cueing paradigm - Simple probe detection experiment: measures RT o Task is to look at a point and not move eyes - Posner o His invention was game changing o Almost the same as the simple probe o Have the star and the target stimulus o In between, Posner showed a slide with an empty box on the left  Box meant to influence attention o If box appears on same side of the target, is called a VALID CUE o If box is on the right side (opposite side) is called an INVALID CUE  Attention involuntarily shifts to the right  Target shows up on left  Response time is slower than even if there was no cue - Difference between valid and invalid cue = cueing effect - Stimulus driven cue or peripheral cue or reflexive cue o Appear at same location as where target will appear o Change in luminence o Stimulus drives shift of attention o Difference is the voluntary cue - Replace fixation point with an arrow pointing one way or another - Arrow = symbolic cue o We know it means it is pointing at something o Is an invalid cue o Could be pointing in either direction - Positive cueing effect – valid cue makes one faster at detecting things - Arrow cues don’t physically direct, but the meaning of the symbol makes us shift our attention - voluntary cues: spatial info conveyed through cognitions and memory, often based on language or other symbols - Diff between stimulus driven and voluntary cues: stimulus driven don’t have to predict the targets in reliable ways o Box does not really predict where it is o Use stimulus driven cues no matter what, even if they do not mean anything o Ex. arrows are so well learned that we cannot help but look at them - Cueing effects reveal important differences between stimulus driven and voluntary cues: physiologically, they do different things - There is evidence that the two mechanisms that drive shifts in attention are the same but not completely Stimulus onset asynchrony (SOA) : time between the onset of a stimulus and the onset of another – time delay between two stimuli - Benefit more from valid cues over time - 20 second delay for peripheral cues, takes longer for symbolic cues - These curves continue longer than 400 ms o Symbolic stays straight o Peripheral cues go below zero as time passes  Negative cueing effect  after longer delay and more time has passed, slower on the valid side than the invalid side  called IOR – inhibition of return demo of face - focus on face - because eyes are facing a certain way, pay more attention to the side it is looking in - important social cue  when people are looking at something, is a cue we should pay attention to it too Overt shifts of attention - a shift of attention accompanied by corresponding movements of the eyes covert shifts of attention: shift of attention in the absence of corresponding movements of the eyes Perceptual biases: asymmetries in perfection of the left and right of stimulus Ex. picture – half man half woman – people usually say the bottom looks more like a woman - attention is more biased to the left side - therefore, the face with the female face on the left side seems like the more womanly face Line bisection task - horizontal line with a vertical line in the middle - need to say if it looks more to the left or more to the right - systematically say it looks like it is more on the right side - if we have to choose where to put the vertical line, more likely to put it closer to the left side grating scales task - task is to tell which of the two rectangles has more of the thinner stripes - even if pictures are symmetrical, tend to pick stimulus with thin strips on the LEFT side space-based cueing of attention (non-spatial) feature based cueing - ex. colour - if attention is based on some non-spatial feature, we have the feature to become more visible throughout the visual field o ex. thinking of the colour red  becomes more salient demo of where’s waldo - if using stripes to look for waldo, there are many stripes in the picture anad become more salient - so many other things share features with him Z
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