Task difficulty and specificity of
perceptual learning
Ahissar, Hochstein (1997) Nature
Final session
2nd third
1st third
Task difficulty
Stimulus-to-mask onset asynchrony
Easy task:
Learning was general,
Complete transfer when swapping
-> position non-specific
Classical view of visual hierarchy:
1. Complexity of receptive field - hierarchical
2. Parallel stream – dorsal vs ventral
3. Learning (experience)-, attention (context)dependent processing (feedback)
only at higher areas, but recently down to V1
Reverse Hierarchy Theory of Visual Perception
Two modes of perception
1
Rapid, generalized perception
“vision at a glance”
Slow detailed perception
“vision with scrutiny”
2
Automatic, implicit
Categorical scene
interpretation : pop-out
Conscious, attentive
Attention to details
Learning effect transfer
Condition-specific
Feedforward processing
Hierarchical
Feedback processing
Reverse hierarchical
3
Reverse
hierarchy
theory
Common view:
Vision at a glance – effortless simple feature detection
- low-level mechanism
Vision with scrutiny – high-level
Pop-out for complex feature (shading, etc) challenge this idea
Reverse Hierarchy Theory:
Vision at a glance – initial, crude, global percept, e.g., pop-out
– high-level cortical mechanism
- early spread attention – large receptive field
Vision with scrutiny – focused attention, low-level
- when focused attention, inattentional blindness
Early spread attention, high cortical level determination of initial conscious perception
Change blindness
Initial conscious perception acquire gist of scene.
Later focused attention grasps low-level detail.
Vision at a glance vs vision w/ scrutiny
Pop-out for complex features
Problem: what is high and low level?
Problems Reverse Hierarchy Theory:
1. Hierarchy is poorly defined from connection pattern.
Low-level vs high-level
Pop-out with shading may be still low-level.
2. Sharp tuning for feature/space is not necessarily
mean superior discrimination.
See population coding.
3. Attention effects with large receptive fields - Desimone
Perception – parallel processing
by M. Sereno
Two streams of visual processing
Neural activity in early visual cortex reflects
behavioral experience and higher-order
perceptual saliency
Nature Neuroscience (2002)
Top-down reentry of later involvement of low-level area