Task 5 Flashcards
(14 cards)
Explain the Goodale & Milner Two Pathway Model
There are two pathways that integrate visual information into relevant actions:
Ventral stream (infero temporal cortex) is responsible for recognizing & intepreting visual inputs. It is related with visual memories and planning of actions to be used offline (when visual stimuli are not available).
The dorsal stream (posterior parietal cortex) is responsible for actions in real time. It uses visual inputs received from the ventral stream to guide these online movements.
What are the evidence for the ventral & dorsal pathway?
Severe visual agnosia: Impairments in visual recognition but can perform visually guided reaching (impaired ventral stream dorsal stream in tact).
Optic ataxia: Has visual memory but no ability to adapt visually guided actions in real time (impaired dorsal stream but intact ventral stream)
study on monkeys: Visually guided behaviors (e.g. reaching) activated different classes of neurons in dorsal stream. Grasping neurons were not related with shape/size of objects.
Describe the patient who had severe visual agnosia
She had a brain damage due to carbon monoxide poisoning which damged her cortical visual areas. Damaged the ventral stream
She could not recognize that were in front of her & could not copy them (e.g. an apple). But she could draw from memory.
Card slot orientation test:
She was asked to look at the slot and orient the envelop to she shape of the slot - she could not do it right.
When asked to post the envelop in the slot she got it right.
Describe the patient with optic ataxia
The patient had difficulties to point towards or grasp object presented to him but had no difficulties touching his body part
What are scale errors?
A child’s attempt to perform actions that is usually performed on a normal size object to a smaller one
What are the four criterias of scale errors?
- Partial or full attempts to perform action on a smaller version of a larger object (e.g. sitting on miniature chair)
- Relevant part of body for the action came into contact with miniature object.
- Behaviour was a serious attempt – not pretend play
- Persistent action.
When does the ventral and dorsal pathway develop in infants and when is it disintegrated?
It is present at 13 months but appears to disintegrate between 13 to 40 months
Why do scale errors occur?
- Momentary failure of inhibitory control
- Immature body self-awareness of very young children
- Perception-action (dorsal & ventral stream) dissociation/immaturity
- It is not a result of an inability to discriminate between size – size discrimination emerges from 4.5 months
- Due to immature PFC – Lack of inhibitory control over the motor plan.
Explain scale errors using the ventral and dorsal model
Ventral stream:
* Recognition of the miniature object activates their representations of the larger replicas. (visual memory)
* This also activates motor plan for larger objects.
* Now they use the motor plan for the large object to interact with the miniature object. (off-line actions)
Dorsal stream:
* As they approach the miniature object, they use the visual info about it (actual size) to recalibrate their actions (on line motor planning).
So there is a dissociation between the two pathways.
What were the three conclusions from DeLoache’s study?
- Scale errors & pretend play are distinguishable by naïve observers.
- Pointing out small size of objects did not decrease frequency of scale errors.
- Priming children to make more scale errors did not increase their frequency.
How did DeLoache explain his results when he did the chair priming condition?
- Momentary failure of inhibition may explain scale errors despite labelling.
- Reverse priming may have occurred: being exposed to chairs may have made them aware of the actual sizes of the miniature chairs.
- Habituation to chairs thus preference for the new objects.
- Method differs from previous studies: prev studies = longer time frames (6 months), more tasks given
DeLoache had 4 experiments to measure scale errors. What were the experiments about?
Experiment 1: scaled errors vs. pretend play
Experiment 2: can independent scorers identify scale erros?
Experiment 3: does labelling the size diminish scale errors?
Experiment 4: does priming increase scale errors?
One study investigated if scale errors are made when children use dolls to interact with toys. There were three groups of children: young (16-24 months), middle (29 to 32 months) and older (35-40 months).
Why did older infants make more scale errors?
More scaled errors observed in this study that DeLoache (2013) probably because the difference in sizes in a doll’s large objects & small are not much compared to that of a child’s object and its miniature version. plus they also spent more time playing with the dolls.
What are the differences & similarities between the perception/action and planning/control model?
Similarity: perception are served by the ventral stream
Differences:
- planning/action assume that planning is through the medial visual stream that leads to the parietal lobe, and online action are via the dorsal stream.
-Perception/action assume that both planning and control are through the dorsal stream
