Chapter 10: Perception and Action

Overview of Questions How does the way the environment “flows by” a moving car help the driver stay on the road? How can an outfielder know where to run to get under a fly ball? How do neurons in the brain respond when a person performs an action and when the person watches someone else perform the same 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 Unable to provide an explanation for how pilots used environmental information to land airplanes

The Ecological Approach to Perception - continued Types of information used by perceivers as they move through an 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 (You control it!) –Invariant information - properties that remain constant while the observer is moving

Flying OverLanding

Types of Information from the Environment Texture gradients: –Occur when equally spaced elements appear to be more closely packed as distance from the observer increases –Provide invariant information Affordances: –Information from the stimulus that specifies how it can be used

Do People use Flow Information? Experiment by Land and Lee –Car fitted with instruments to measure Direction of gaze of driver –When driving straight, driver looks straight ahead but not at focus of expansion 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

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

Flow, Posture, and Balance Experiment by Lee and Aronson –13- to 16-month-old children in “swinging 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 –Adults show the same response as children when placed in the swinging room

The Physiology of Navigation Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patterns Probably affected in the spiral illusion 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 specify directions of flow patterns –Judgments were shifted in the direction of the stimulated neuron

Figure Monkey brain, showing key areas for movement perception and visual-motor interaction. IT = inferotemporal cortex; MT = medial temporal area; MST = medial superior temporal area.

Skilled Actions Somersaulting (backflips) –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

Skilled Actions - continued Catching a fly ball –This could be performed by determining speed and angle of the rise and then calculating the parabolic arc –McBeath et al. found that ball players use linear optical trajectory (LOT) Outfielders run in a slightly curved path so that the ball is directly above them Dogs chasing Frisbees show the same behavior

Responding of Neurons in the Parietal Lobe Visual-dominant neuron - responds best when a monkey looks at a button or pushes it in the light Motor-dominant neuron - responds best when pushing button both in light and dark –Does not respond to looking at a button Some neurons respond best to looking and manipulating objects

Figure Two types of parietal neurons that respond to visual and motor tasks. See text for details. (From H. Sakata, M. Taira, M. Kusunoki, A. Murata, and Y. Tanaka (1977). The parietal association cortex in depth perception and visual control of hand action. Trends in Neurosciences, 20, p Adapted with permission.)

Parietal Reach Region Neurons in the posterior parietal cortex show –Response before monkeys grasp an object These neurons signal the intention to grasp Neurons from this region send signals to the premotor area –These neurons respond to carrying out actions and to observing others carrying out the same actions

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 Mirror neurons may help link sensory perceptions and motor actions

Figure Response of a mirror neuron. (a) Response to watching the experimenter grasp food on the tray. (b) Response when the monkey grasps the food. (c) Response to watching the experimenter pick up food with a pair of pliers. (From G. Rizzolatti, et al., Cognitive Brain Research, 3, p Adapted with permission from Elsevier Science.)

Mirror Neurons and Social Interaction Autism has been associated with decreased mirror-neuron function Autism is associated with poor social skills, possibly due to an inability to put oneself in another’s situation Please see article linked below: