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Chapter 7: Taking Action. The Ecological Approach to Perception. Approach developed by J. J. Gibson (began in late 1950s) Gibson felt that traditional laboratory research on perception was: too artificial - observers were not allowed to move their heads.
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The Ecological Approach to Perception • Approach developed by J. J. Gibson (began in late 1950s) • Gibson felt that traditional laboratory research on perception was: • too artificial - observers were not allowed to move their heads. • unable to provide an explanation for how pilots used environmental information to land airplanes
The Ecological Approach to Perception - continued • Optic array - structure created by the surfaces, textures, and contours in the environment • Optic flow - appearance of objects as the observer moves past them • Gradient of flow - difference in flow as a function of distance from the observer • Focus of expansion - point in distance where there is no flow
Optic Flow • Self-produced information - flow is created by the movement of the observer • Invariant information - properties that remain constant while the observer is moving • optic flow demo
Figure 7.2 The relationship between movement and flow is reciprocal, with movement causing flow and flow guiding movement. This is the basic principle behind much of our interaction with the environment.
Self-Produced Information - Keeping your Balance • Experiment by Lee and Aronson • 13- to 16-month-old children placed in “swinging room” • In the room, the floor was stationary but the walls and ceiling swung backward and forward. • The movement creates optic flow patterns. • Children swayed back and forth in response the flow patterns created in the room.
Experiment by Lee and Aronson - continued • Adults show the same response as children when placed in the swinging room. • Results show that vision has a powerful effect on balance and even overrides other senses that provide feedback about body placement and posture.
Figure 7.4 Lee and Aronson’s swinging room. (a) Moving the room toward the observer creates an optic flow pattern associated with moving forward, so (b) the observer sways backward to compensate. (c) As the room moves away from the observer, flow corresponds to moving backward, so the person leans forward to compensate, and may even lose his or her balance. From Lee, D. N., & Aronson, E., (1974).Visual proprioceptive control of standing in human infants. Perception and Psychophysics, 15, 529-532.
Self-produced Information - Somersaulting • Somersaulting • Could be performed by learning a predetermined sequence of moves; thus performance would be the same with and without vision • Bardy and Laurent found that expert gymnasts performed worse with their eyes closed. • They use vision to correct their trajectory. • Novice gymnasts do not show this effect.
Figure 7.3 “Snapshots” of a somersault, starting on the left and finishing on the right. From Bardy, B. G., & Laurent, M. (1998). How is body orientation controlled during somersaulting? Journal of Experimental Psychology: Human Perception and Performance, 24, 963-977.
Do People use Flow Information? • Experiment by Land and Lee • Car fitted with instruments to measure • Angle of steering wheel • Speed of vehicle • Direction of gaze of driver • When driving straight, driver looks straight ahead but not at focus of expansion
Experiment by Land and Lee - continued • When driving around a curve, driver looks at tangent point at side of the road • Results suggest that drivers use other information in addition to optic flow to determine their heading. • They might be noting the position of the car in relation to the center line or side of the road.
Figure 7.6 Results of Land and Lee’s (1994) experiment. The ellipses indicate the place where drivers were most likely to look while driving down on (a) a straight road and (b) a curve to the left.
The Direction Strategy for Determining Heading • Visual direction strategy - observers keep their body pointed toward a target • Walkers correct when target drifts to left or right • Blind walking experiments show that people can navigate without any visual stimulation from the environment.
The Physiology of Navigation • Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patterns • Experiment by Britten and van Wezel • Monkeys were trained to respond to the flow of dots on a computer screen. • They indicated whether the dots flowed to the right, left, or straight ahead.
Experiment by Britten and van Wezel • As the monkeys did the task, microstimulation was used to stimulate MST neurons that respond to specific directions of flow patterns. • Judgments were shifted in the direction of the stimulated neuron.
Figure 7.8 Monkey brain, showing key areas for movement perception and visual-motor interaction.
Brain Areas for Navigation • Experiment by Maguire et al. • Observers learned the layout of a “virtual town” • In a PET scanner, they were told to navigate to locations in the town. • Navigating activated the right hippocampus and part of the parietal cortex. • Activation was greater when the navigation between points was accurate than when it was inaccurate.
Figure 7.11 (a) Scene from the “virtual town” viewed by Maguire et al.’s (1998) observers. (b) Plan view of the town showing three of the paths observers took between locations A and B. Activity in the hippocampus and parietal lobe was greater for the accurate path (1) than for the inaccurate paths (2 and 3).
Experiment by Spiers and Maguire • London cab drivers played an interactive computer game with accurate depictions of London streets. • They were given instructions to drive towards a destination. • In mid-route, the destination was changed. • They also heard a statement unrelated to the destination.
Experiment by Spiers and Maguire - continued • The cab drivers’ brain activity was measured by fMRI during their “trip.” • After the trip was finished, they viewed a playback and were asked what they were thinking at different points. • The results showed a link between brain activation and specific navigation tasks.
Figure 7.13 Patterns of brain activation in the taxi drivers in Spiers and Maguire’s (2006) experiment. The descriptions above each picture indicate what event was happening at the time the brain was being scanned. For example, “customer-driven route planning” shows brain activity right after the passenger indicated the initial destination. The “thought bubbles” indicate the drivers’ reports of what they were thinking at various points during the trip.
Affordances - What Objects are for • Gibson believed affordances of objects are made up of information that indicates what an object is used for. • They indicate “potential for action” as part of our perception. • People with certain types of brain damage show that even though they may not be able to name objects, they can still describe how they are used or can pick them up and use them.
Affordances - What Objects are for - continued • Experiment by di Pelligrino et al. • Tested woman with damage to parietal lobe who showed extinction - the inability to direct attention to more than one thing at a time • Two cups were presented; one to the right and one to the left • The left cup was not detected unless there was a handle added. • Researchers concluded that the affordance for grasping was activating a different part of the brain.
Physiology of Reaching and Grasping • Neurons in the parietal lobe that are silent when a monkey was not behaving, fire when the monkey reached to press a button to receive food. • This response only happened when the animal was reaching to achieve a goal. • Calton et al. identified goal directed neurons in the parietal reach region (PRR)
Physiology of Reaching and Grasping - continued • Experiment by Connolly - evidence for PRR in humans • Experimental condition - observers looked a fixation point and were given a cue for the location of a target • After a nine-second delay, they pointed at the target • Control condition - a nine-second waiting period occurred, then the cue appeared and the observer pointed at the target
Figure 7.16 (a) Procedure for Connolly’s (2003) experiment. The observer looks at the fixation point (+), and the target (o) appears off to the side. (b) Activation of the PRR during the 9-second delay or during the waiting period. See text for details.
Experiment by Connolly - continued • During the nine-second delay or waiting period for both conditions, fMRI was used to measure activity in the PRR • Results showed higher activity during the nine-second delay than in the nine-second waiting period • This suggests that the PRR encodes information related to the intention for movement to a location.
Mirror Neurons in Premotor Cortex • Neurons in the premotor cortex of monkeys that • Respond when a monkey grasps an object and when an experimenter grasps an object • Response to the observed action “mirrors” the response of actually grasping • There is a diminished response if an object is grasped by a tool (such as pliers).
Mirror Neurons in Premotor Cortex - continued • Possible functions of mirror neurons • To help understand another animal’s actions and react to them appropriately • To help imitate the observed action • Audiovisual mirror neurons - respond to action and the accompanying sound • Mirror neurons may help link sensory perceptions and motor actions.
Figure 7.17 Response of a mirror neuron (a) to watching the experimenter grasp food on the tray; (b) when the monkey grasps the food; (c) to watching the experimenter pick up food with a pair of pliers. From Rizzolatti, G., Forgassi, L., & Gallese, V. (2000). Cortical mechanisms subserving object grasping and action recognition: A new view on the cortical motor functions. In M. Gazzaniga (Ed.), The new cognitive neurosciences (pp 539-552). Cambridge, MA: MIT Press.
Figure 7.18 Response of an audiovisual mirror neuron to four different stimuli. From Kohler, E., Keysers, C., Umilta, M. A., Fogassi, L., Gallese, V., & Rizzonatti, G. (2002). Hearing sounds, understanding actions: Action representation in mirror neurons. Science, 297, 846-848.)
Predicting People’s Intentions • Experiment by Pierno et al. • Observers watch three four-second videos • Grasping condition • Gaze condition • Control condition • Response of the neurons in the human action observation system was measured in a brain scanner.
Figure 7.20 Results of Pierno et al.’s (2006) experiment showing the increase in brain activity that occurred for the three conditions shown in Figure 7.19 in (a) the premotor cortex and (b) an area in the frontal lobe.
Mirror Neurons and Experience • Experiment by Calvo-Merino et al. • Tested three groups • Professionally trained ballet dancers • Professionally trained capoeira dancers • Control group of non-dancers • They watched two videos • One with standard ballet movements • One with standard capoeira movements
Mirror Neurons and Experience - continued • Activity in the premotor cortex was measured while they watched the videos. • Results showed PM activation was • Greatest for ballet dancers while watching ballet • Greatest for capoeira while watching capoeira • Same response for both for non-dancers
Figure 7.22 Results of Calvo-Merino’s (2005) experiment, showing increase in activity in PM cortex. Black bars = response to ballet films, white bars = response to capoeria films.
Two Approaches for Neural Prostheses • The goal is for people with spinal cord injuries to be able to move a computer mouse directly with their thoughts. • Hochberg et al. - used signals sent from motor cortex of a person through a computer to position cursor • Musallam et al. - used activity from PRR of a monkey through computer to position computer
Two Approaches for Neural Prostheses - continued • Problems with these approaches • Less accurate and more variable control than actual muscle movement • Devices only use signals from a small group of neurons • Researchers need to determine which signals are most important for the desired movement
