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.

• 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

Figure 7-1 p154

Figure 7-2 p154

Self-produced Information

• 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 p155

Figure 7-4 p155

The Senses Do Not Work in Isolation

• 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.

The Senses Do Not Work in Isolation - 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 7-5 p156

Navigating Through the Environment

• 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.

Figure 7-6 p157

Figure 7-7 p157

Figure 7-8 p158

Navigating Through the Environment - continued

• 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 7-9 p158

Driving a Car

• 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 7-10 p159

Walking

• 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.

Figure 7-11 p159

Figure 7-12 p160

Wayfinding

• Landmarks involved taking routes the involves making turns

• Landmarks are objects on the route that serve as cues to indicate where to turn.

Figure 7-13 p160

Figure 7-14 p161

Wayfinding - continued

• Experiment by Janzen and van Turennout

– Observers studied a film that moved through a “virtual museum.”

– They were told that they should be able to act as a guide within the museum.

– Exhibits appeared both at decision points where turns were necessary and non-decision points.

Experiment by Janzen and van Turennout - continued

• Observers were given a recognition task while in an fMRI.

– They were presented objects they had seen as exhibits, and ones they had not seen.

• Results showed the greatest activation for objects at decision points (landmarks) in the parahippocampal gyrus.

Figure 7-15 p161

Effects of Brain Damage on Wayfinding

• Retrosplenial cortex damage

• Maguire (2006)

– Patient T. T.

– Parahippocampus gyrus

– Retrosplenial cortex

– Hippocampus

Figure 7-16 p162

Figure 7-17 p162

Affordances - What Objects Are Used 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.

The 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.

Figure 7-18 p164

The Physiology of Reaching and Grasping - continued

• Experiment by Connolly - evidence for PRR in humans

• Fattori – three different regions are used in grasping

• Schindler – obstacle avoidance is controlled by the parietal regions

Figure 7-19 p165

Figure 7-20 p165

Figure 7-21 p166

Mirroring Others’ Actions in the Brain

• Mirror neurons in the 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.

Video: Mirror Neurons

Figure 7-22 p167

Figure 7-23 p167

Predicting People’s Intentions

• Iacoboni (2005) – mirror neurons can be influenced by different intentions

Figure 7-24 p168

Figure 7-25 p168

Action-Based Accounts of Perception

• The traditional approach to perception is focused on how the environment is represented in the nervous system

• According to action-based accounts of perception the purpose of perception is to create a representation in the mind of whatever you are looking at