Lec 8 | MIT 9.00SC Introduction to Psychology, Spring 2011
MIT OpenCourseWare・2 minutes read
The lecture explores human attention limitations and introduces attention disorders like blindsight and neglect, demonstrating how some individuals subconsciously perceive visual stimuli despite lacking conscious awareness. Through various experiments and case studies, it illustrates the complexities of these disorders, revealing that unconscious processing can still occur in the presence of significant brain damage.
Insights
- The lecture highlights the limitations of human attention, illustrating how much information we miss in our environment, with some stimuli entering our awareness unconsciously, as demonstrated through the conditions of blindsight and neglect.
- Blindsight is a fascinating phenomenon where individuals, despite being cortically blind, can respond to visual stimuli without conscious awareness, suggesting that the brain has an unconscious processing system, particularly involving the superior colliculus.
- The text discusses neglect, a disorder where individuals fail to acknowledge one side of their environment, as exemplified by a woman who only eats from the right side of her plate after a stroke, showcasing the profound impact of neurological injuries on spatial awareness.
- Experimental findings reveal that even when patients with neglect do not consciously perceive objects on their neglected side, their brains still process some information, as evidenced by their ability to report differences in objects when they are not identical, indicating a complex interplay between awareness and unconscious processing.
Get key ideas from YouTube videos. It’s free
Recent questions
What is visual neglect?
Visual neglect is a neurological condition where individuals fail to notice objects or stimuli on one side of their visual field, typically the left side, due to damage in the right hemisphere of the brain. This condition often arises after strokes or brain injuries and is characterized by a lack of awareness of the neglected side, leading to significant challenges in daily activities. Patients may demonstrate this neglect by ignoring the left half of their environment, such as only eating from the right side of a plate or failing to acknowledge items on the left when asked to report what they see. The phenomenon of "extinction" can also occur, where patients can perceive stimuli on both sides when presented separately but struggle to notice those on the neglected side when both sides are shown simultaneously. This condition highlights the complexities of spatial awareness and cognitive processing in the brain, revealing how neurological impairments can profoundly affect perception and behavior.
How does blindsight work?
Blindsight is a fascinating phenomenon where individuals who are cortically blind due to damage in the primary visual cortex can still respond to visual stimuli without conscious awareness. This suggests that there are alternative pathways in the brain that process visual information outside of conscious perception. For instance, the superior colliculus, part of the brain involved in reflexive eye movements, plays a crucial role in this unconscious visual processing. Patients with blindsight can accurately guess the location or characteristics of objects in their blind field, even though they claim to see nothing. Historical experiments with animals, such as dogs with bilateral occipital lesions, demonstrated that they could navigate their environment despite being cortically blind, indicating that some level of visual processing occurs unconsciously. This phenomenon challenges our understanding of perception and consciousness, revealing that the brain can still process visual information even when individuals are not consciously aware of it.
What is anosognosia?
Anosognosia is a neurological condition in which individuals are unaware of their own disabilities or impairments, often resulting from brain injuries or strokes. Patients with anosognosia may deny having a problem, even when it is evident to others. For example, a patient with paralysis on one side of the body might insist that their affected limb is functioning normally. This disconnect arises because the brain injury impairs the patient's ability to construct a reality that acknowledges their condition, despite their cognitive capacity to understand it. Anosognosia can complicate rehabilitation efforts, as patients may not recognize the need for treatment or assistance. The condition highlights the intricate relationship between self-awareness and neurological function, illustrating how brain damage can lead to profound gaps in a person's understanding of their own health and capabilities.
How do infants develop visual attention?
Infants develop visual attention through a gradual maturation of their visual processing systems, which is evident in their eye movements and responses to stimuli. Research has shown that even very young infants can identify and respond to visual stimuli in both their "good" and "blind" visual fields. As they grow, particularly between 8 to 12 weeks of age, their ability to focus and compete for visual attention becomes more refined. In experiments, infants consistently moved their eyes toward stimuli in both fields when there was no competition for attention. However, when a fixation dot was introduced, their likelihood of noticing stimuli in the blind field decreased, indicating that as their cortical systems mature, their conscious attention becomes more selective. This developmental shift suggests that the conscious visual processing capabilities of infants evolve over time, leading to a more sophisticated understanding of their visual environment as they grow.
What is the role of the superior colliculus?
The superior colliculus is a critical structure in the brain that plays a significant role in visual processing and attention, particularly in the context of reflexive eye movements and unconscious visual perception. It is involved in directing gaze and coordinating eye movements toward stimuli in the environment, even when individuals are not consciously aware of those stimuli. In cases of blindsight, for instance, the superior colliculus allows individuals to respond to visual cues in their blind field, suggesting that it processes visual information outside of conscious awareness. This structure connects the retina to various brain regions, facilitating the rapid processing of visual information and enabling quick reflexive responses. The superior colliculus thus serves as an essential component of the visual pathway, highlighting the complexity of how the brain integrates sensory information and directs attention, even in the absence of conscious perception.