Interacting with Objects

Ecological approach to perception

Focuses on specifying the info in the environment that is used for perception

Emphasizes the study of moving observers to determine how their movement results in info that creates perception and guides further movement

Optic flow

Flow of stimuli in the environment that occurs when an observer moves relative to the environment

Forward movements cause an expanding optic flow

Backwards movements cause a contracting optic flow

2 characteristics of optic flow

Gradient flow

Focus of expansion (FOE)

Gradient flow

Optic flow is rapid in the foreground and becomes slower as distance from the observer increases

Focus of expansion

The destination toward where the observer is moving and has an absence of flow

Invariant information

Environmental properties that do not change as the observer moves relative to an object or the scene

Affordances

Info that indicates how the stimulus can be used

Kretch and Adolph (2013)

Experience matters for affordances

Crawling and walking infants ability to perceive affordances for locomotion

Experiment 1

• Participants are 12 months old 

  • Some were experiences crawlers (M=16 weeks)

  • Some were novice walkers (M=5 weeks)

• Set up

  • Tested approaching drop-offs of 1cm-90cm

  • Crawlers on hands-knees walkers on 2 feet

  • Caregiver encouraged infant to move toward them and the cliff

• Results

  • 1cm - all walked or crawled over it

  • Other cliffs

    • Experienced crawlers attempted crawling over it within ability, at 90 cms none tried crawling over it

    • Novice walkers – tried to walk over cliffs across the heights, even 50% of trails at 90cm

Experiment 2

• Participants: 18 months

more info?

Landmarks

Objects that serve as cues in wayfinding

Helpful in navigation

Decision-point landmarks vs non-decision-point landmarks

More likely to remember decision-point landmarks than non-decision point landmarks

Brain parts involved in navigation

Hippocampus and parahippocampal gyrus

Place cells

Neurons in the hippocampus that fire only when an animal is in certain place in the environment

Grid cells

Cells in the entorhinal cortex that fire when an animal is in a particular place in the environment, with multiple fields in a grid-like pattern

Maguire et al (2006)

About hippocampus structure and navigation

Taxi cab drivers vs Bus drivers in london

Results:

Taxi drivers scored higher than bus drivers on landmark tasks

Taxi drivers had larger posterior hippocampus and smaller anterior hippocampus than bus drivers

Janzen & van Turrenout (2004)

Participants watched a virtual maze of a museum

Recognition tests for objects, measured brain activity in the parahippocampal gyrus

Results: greater brain activity for objects at decision-points than non-decision-points

Schinazi & Epstein (2004)

Participants were asked to do real-world route learning on the UPenn campus

Brought into lab and measured behavior and brain activity

Results:

Difference in accuracy and recognizing buildings

• Decision-point buildings were better remembered than non-decision-point buildings

Size-weight illusion

Error in predicting weight when observing two differently sized objects that have the same weight —> results in us having a mismatch of force for the actual weight of the object

Parietal Reach Region

Areas in the parietal cortex that are involved in reaching behavior