Attentive Processing and Long-Term Memory

    Once in working memory, the cyclist interprets the blue shape's meaning by finding information in another area of memory called "Iong-term" memory. This is the permanent store of information and knowledge that we all carry around in our heads. 
    Recall that attention can be controlled automatically or purposefully. Some retrieval from long-term memory (as when recognizing a familiar object) seems to occur automatically with little or no attentional expenditure. However, sometimes we actively search memory (as when trying to recall instructions or making plans). This requires attentional resources and adds a load to working memory. In other words, thinking or recalling information can also cause information to be lost from working memory. 

    So, what could have led Mr. Z to Collide with Ms. Y?

    In the hypothetical situation described previously, the accident would not have occurred if everything had worked properly. Mr. Z would have 

    - detected Ms. `Cs blue coat or white hat as a blob; 

    - turned his eyes toward her to define the shape; 

    - retrieved the necessary information from memory to identify the shape as a person;

    - made the decision to apply brakes, and; 

    - applied the brakes. 

    From this reference the starting point of any visual analysis is the question: Should Mr. Z have detected Ms. Y? After all, if the conditions would have made Ms. Y undetectable at the sensory level (it was too dark, etc.), then no further information processing would have been possible. 

    A visibility analysis would note that Ms. Y was wearing a dark blue coat, which would have little contrast against the dark background existing at 9:00 PM. On the other hand, the white hat would show up very well. The hat is unfortunately small compared to the coat and might still be less visible than the coat. Of course, if the background were bright. say a brightly illuminated shopping strip, then the dark coat might be highly visible and the white hat relatively hard to see. 

     

     

    If Mr. Z were looking straight ahead or perhaps searching for the proper street sign, Ms. Y would likely be seen only in the low resolution peripheral field as she steps off the curb. This significantly increases the contrast needed to see her. Lastly, the contribution of some environmental factors is very difficult to estimate numerically. More often than not, there is no simple way to factor in the effects of background masking, cyclist light adaptation, odd shapes, etc. 

    Now for the cyclist. Mr. Z is 55 years old, so there is an age loss of contrast sensitivity, a factor of about 1.8. Moreover, he had had a few beers, so his blood alcohol level was .06. Although this is below the legal limit, research shows that .06 is a high enough BAC to seriously impair vision. This is an important point to remember for litigation: even though a cyclist is within legal limits, he may still be functionally impaired, especially if there are negative environmental factors such as low lighting or poor roadway design. In addition, was he wearing optical correction? Was the correction correct? Does he have any eye disorders?
     
    Mr. Z knows that pedestrians probably cross at intersections and has developed an expectation that pedestrians, if they appear, are likely to be there. He would not expect to see Ms. Y cross in the middle of the block, further decreasing detectability. If Mr. Z had frequently driven down the same stretch of highway and never seen a pedestrian there before, then his expectations would be even greater that no pedestrian was likely to appear. 

    In this case, there are many factors, which would make Ms. Y difficult to see: the low light level of night time driving, Ms. V's dark coat produced low contrast (assuming a black background), her location in the peripheral field, the driver's age, his blood alcohol level, and his expectations. 

    Now for the cyclist. Mr. Z is 55 years old, so there is an age loss of contrast sensitivity, a factor of about 1.8. Moreover, he had had a few beers, so his blood alcohol level was .06. Although this is below the legal limit, research shows that .06 is a high enough BAC to seriously impair vision. This is an important point to remember for litigation: even though a cyclist is within legal limits, he may still be functionally impaired, especially if there are negative environmental factors such as low lighting or poor roadway design. In addition, was he wearing optical correction? Was the correction correct? Does he have any eye disorders?
     
    Mr. Z knows that pedestrians probably cross at intersections and has developed an expectation that pedestrians, if they appear, are likely to be there. He would not expect to see Ms. Y cross in the middle of the block, further decreasing detectability. If Mr. Z had frequently driven down the same stretch of highway and never seen a pedestrian there before, then his expectations would be even greater that no pedestrian was likely to appear. 

    In this case, there are many factors, which would make Ms. Y difficult to see: the low light level of night time driving, Ms. V's dark coat produced low contrast (assuming a black background), her location in the peripheral field, the driver's age, his blood alcohol level, and his expectations. 

    Let's assume that Ms. `I's contrast level were above detection threshold. The next step is to assess the likely operation of attention and working memory. We would want to look at all sources of input to working memory and to examine any factors affecting Mr. Z's attentional capacity. 
    All of these factors would combine to stress attentional capacity. The large number of information sources (visual, radio, recall) and Its visibility conditions would overload attention. so some information could be ignored. Since he would probably be looking either directly ahead or up at street signs, the chances of seeing Ms. Y, crossing at an unexpected location in the middle of the block, would be very poor. 

    The fast riding would cause working memory to continually fill and require the rapid loss of old information. It is quite possible that Mr. Z could have looked directly at Ms. Y but still not recall seeing her either because the information was filtered out due to attention being allocated elsewhere (listening to the radio, recalling directions, planning the next turn, etc.) or was displaced from working memory before it could be properly interpreted and stored in long-term memory. 

    Moreover, factors lowering Mr. Z's attentional capacity undoubtedly contributed to the accident. At 55 years old, his age probably had a modest effect. The .06 BAC also likely contributed to lowering his attentional capacity. 

    Conclusion

    The main purpose of this explanation and hypothetical example in this section is to show you how limited the human information processing system is and how it can be overwhelmed and not capable of making the right decision at the right time to avoid or minimize an accident from happening. 

    The accident could easily have been caused by a large number of factors working in concert disable the system such as the cyclist being in hurry, his age, attention being shared across several inputs (radio, road and recall), moderate blood alcohol level, uncertainty about the directions and unfamiliarity with the street. Factors such as headlight glare and optical correction may have also played a role. Ms. `Cs low visibility clothing also contributed by making her less conspicuous, even if she was above detection threshold. Lastly, she crossed the street at an unexpected location, further making detection more difficult.