Lecture 11 Flashcards
3 examples of motion
1) An object moves, and the observer is stationary
2) An object moves, and the observer follows the object with their eyes
3) An observer moves their eyes through- scans- a stationary environment
The situation/example of motion where you look straight as an object moves past… object, eyes, images of observer’s retina, object movement perceived
object: moves
eyes: stationary
image of observer’s retina: moves
object movement perceived?: yes
The situation/example of motion where you follow a moving object with eyes… object, eyes, images of observer’s retina, object movement perceived
object: moves
eyes: move
images of observer’s retina: stationary
object movement perceived?: yes
The situation/example of motion where you look around the room… object, eyes, images of observer’s retina, object movement perceived
object: stationary
eyes: move
images of observer’s retina: moves
object movement perceived?: no
ecological approach
focusses on what/how information directly available in the environment is useful to guide perception/action
optic array
structure created by surfaces, textures, and contours in the environment, which change as the observer moves through space
Gibson thought that optic array can be used to explain when motion is and is not perceived with reference to 2 basic kinds of changes …
1) Local disturbances in the optic array
2) Global optic flow
Local disturbances in the optic array
objects moving relative to background e.g. such that portions of stimuli are periodically covered and uncovered- background and objects
Global optic flow
overall movement of the entire optic array (as a complete whole i.e. without any local disturbances)
If the optic array changes in a uniform way i.e. entirety of optic array all moves in exactly same way, then motion ___ be perceived
If the optic array changes in a uniform way i.e. entirety of optic array all moves in exactly same way, then motion will not be perceived
Perceiving motion
when one part of the visual scene moves relative to the rest of the scene
Not perceiving motion
when the entire field moves, or remain stationary
Corollary discharge theory
hypothesizes that movement depends on 3 signals: 1) Image displacement signal (IDS), 2) Motor signal (MS), 3) Corollary discharge signal (CDS)
Image displacement signal (IDS)
movement of image stimulating receptors across the retina
Motor signal (MS)
signal sent to eyes to move eye muscles
Corollary discharge signal (CDS)
derived from the motor signal (essentially a ‘carbon copy’ of whatever the motor signal is doing, though it gets sent to a different part of the brain for another purpose)
Movement is perceived when comparator receives input from EITHER (but not both)…
corollary discharge signal or image displacement signal
Movement is NOT perceived when comparator receives input, at the same time, from BOTH…
corollary discharge signal and image displacement signals
Real-movement neurons found in monkeys..
responds when a stimulus moves but not when the eyes move
Reichardt detectors
model of a simple neural circuit that could fire in response to movement in one direction
Output unit
compares the signals it receives from two neurons to determine whether they are synchronized i.e. received at exactly the same time
delay unit
slows down the speed of transmission of the signal to the output unit
If the timing is right, and the delay unit ‘__’ the signal from neuron A until the signal from neuron B naturally arrives at the output unit, that output unit will ____ and rightward ___ will be perceived
If the timing is right, and the delay unit ‘holds onto’ the signal from neuron A until the signal from neuron B naturally arrives at the output unit, that output unit will fire and rightward motion will be perceived
Reichardt detectors are ___, meaning that each one can only detect motion in ___ ___ (need one configuration to register leftward motion, and a slightly different one to register rightward motion)
Reichardt detectors are directional, meaning that each one can only detect motion in one direction (need one configuration to register leftward motion, and a slightly different one to register rightward motion)
Perception of motion begins in ___ ___ (___), the region of the occipital lobe where information from the retinas first reach the cortex
Perception of motion begins in striate cortex (V1), the region of the occipital lobe where information from the retinas first reach the cortex
Complex cortical cells
respond to movement of the ends of objects
Middle temporal area (MT)
implicated in other aspects of motion perception
Transcranial magnetic stimulation (TMS)
applied to MT in humans disrupts ability to perceive direction in a random pattern of moving dots
shortest path constraint
apparent movement tends to occur along the shortest path between 2 stimuli
Biological motion
self-produced motion of a person or other living organism
Biological motion can help with ___ ___
Biological motion can help with perceptual organization
Point-light walker stimulus
created by placing light on joints of a living organism, which convey their pattern of movement (and thus, conveys biological motion)
Superior temporal sulcus (STS) are more active for ___ motion
Superior temporal sulcus (STS) are more active for biological motion
Grossman et al. found TMS applied to ___ decreased the participants’ ability to detect biological motion
Grossman et al. found TMS applied to STS decreased the participants’ ability to detect biological motion
Striate Cortex (V1) function related to motion
direction of motion across small receptive fields
Middle temporal area (MT) function related to motion
direction and speed of object motion
Medial superior temporal area (MST) function related to motion
processing optic flow; locating moving objects; reacting for moving objects
Superior temporal sulcus (STS) function related to motion
perception of motion related to animals and people (biological motion)
Implied motion is conveyed by…
still pictures that depict an action which involves motion
Representational momentum
implied motion depicted in a photo can be ‘carried out’ or continue in the observer’s mind
Control condition in Freyd’s Implied motion study
same photo as shown before
Time-forward condition in Freyd’s implied motion study
an image that would have happened slightly later than the one they actually saw
Time-backward condition in Freyd’s implied motion study
an image that would have happened slightly earlier than the one they actually saw
participants were found to take longer to respond to __-__ pictures as compared to __- __ pictures
participants were found to take longer to respond to time-forward pictures as compared to time- backward pictures
