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Vision & Action

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Can we apply this to the real world?

  • Yes!
    • The things we have learned about the human visual system can be used to understand how people perform complex motor actions.
    • But how can we do it?

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Can we apply this to the real world?

  • Need more active experiments!
  • But still need to control what we are presenting to the person
    • Use simulations!
    • Let’s look at some of the benefits of this type of research….

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Benefits: Reducing Errors

  • Although we like to blame machines…the fault is almost always with the human operator.
    • 95 out of 100 of driving accidents are caused by driver error.
    • 85 out of 100 aircraft accidents are caused by cockpit crew error.

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Benefits: Improving Performance

  • Improving free-throw shooting in basketball.
  • Making baggage screeners at Sky Harbor better at detecting illegal items.
  • Training military pilots with flight simulators.

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Benefits: Better Designed Products

  • Have you ever wondered if anyone cares about how usable everyday products like cell phones, computers and microwaves are?
    • Often it seems like the answer is “NO”!
    • There are a lot of bad designs out there!

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Examples from Sports, Driving & Aviation..��(Warning: somewhat self-serving ☺)

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Sports: Eye Movements in Baseball

  • Bahill & LaRitz, 1984
    • Studied eye movements in baseball batting using novices and one professional.
    • Are eye movements fast enough to “keep your eye on the ball” ?

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Sports: Eye Movements in Baseball

  • No! Batters lost sight of the ball well before it reached the plate
    • 5.5 feet from the plate for pro.
    • 9-10 feet from plate for novices.

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Sports: Eye Movements in Baseball

  • But, Ted Williams of the Boston Red Sox claimed he could see the ball hit the bat
    • He could even say which lace would be scuffed!
    • How is this possible?

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Sports: Eye Movements in Baseball

  • Bahill & LaRitz found that on some occasions baseball batters use a different strategy:
    • Follow the ball for initial part of flight and predict where it will be when it crosses the plate.
    • Make a saccade eye movement to the predicted location.

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Sports: Illusions in Baseball

  • But what happens if the batter makes the wrong prediction?
    • For example, what if he/she underestimates the speed and predicts the ball will be lower than it actually is?
    • The natural conclusion the batter will be make is that the ball rose as it approached the plate.
    • It is this prediction error that leads to the illusion of the rising fastball
      • It is physically impossible to make a ball rise when thrown overhand.

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Sports: Illusions in Baseball

  • Evidence for this comes from the fact that batters tend to swing under an unexpected fast pitch.

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Sports: Attention in Baseball

  • Gray (2004).
  • What should a baseball batter pay attention to when swinging?
  • Does it depend on how good they are?

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Should I get the Porsche or the Ferrari?

Is my swing fast enough?

The count is 2 balls and 2 strikes.

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Sports: Attention in Baseball

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Sports: Attention in Baseball

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Sports: Attention in Baseball

  • When you are an expert at something, focusing your attention on what your are doing is a bad thing?
    • Interferes with your automated motor procedures

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Just Do It!

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Driving: Motion Aftereffects

  • When we look at repetitive motion (i.e., objects moving in the same direction) the cells in our brain responding to motion get fatigued producing an effect called motion adaptation
    • Adaptation causes us to misperceive the motion of other objects
    • The most famous example is the waterfall illusion
    • Let’s try the demo again…

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Driving: Motion Aftereffects

  • Gray & Regan (2000).
    • there are some situations in driving that involve repetitive visual motion
      • E.g., driving on an open straight road, day-dreaming
    • Maybe motion adaptation effects driving performance?
    • Test in a driving simulator

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Driving Simulator Procedure:

5 min driving on

straight empty road

​

overtake and pass

other cars

(adaptation to expansion)

speed

timing of maneuver

road safety

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Results:

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

-3

-2

-1

0

1

2

3

No Adapt

Adaptation

Overtaking

Delay

TIME HEADWAY sec

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Results: Driving Speed

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25.5

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26.5

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27.5

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28.5

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29.5

30

1

CONDITION

SPEED AT OVERTAKE ONSET m/sec

SPEED AT OVERTAKE ONSET mph

60

65

Curve Driving Baseline

Static Scene Baseline

Adapt Expansion

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Driving: Motion Aftereffects

  • Staring at the road while driving can lead to motion adaptation.
    • causes drivers to initiate overtaking of a lead vehicle substantially later (up to 0.5 sec).
    • causes people to drive faster
  • Occurs because adaptation to expansion causes drivers to overestimate the TTC.
  • Adaptation causes drivers to make decisions that are of higher risk, slower and more variable.

​

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Driving Research: Distraction

  • Is it dangerous to talk on a cell phone while driving?
    • This is just the tip of the iceberg: navigation displays, DVD, internet, email….

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Driving: Cell Phones & Attention

  • Growing belief that cell phones are dangerous because they distract the driver
    • Brazil and Australia have banned their use
    • one of the hottest items in state legislation
  • Also believed that “hands-free” phones reduce the problem.
    • most people believe that the main problems are manual (holding phone & dialing) and taking eyes off the road

​

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Driving: Cell Phones & Attention

  • Redelmeier & Tibshirani (1997)
    • epidemiological study
    • most cited study
    • examined the phone records of 699 drivers who had recently been in an accident
    • examined calls on the day of the accident and the week proceeding
    • are drivers more likely to have an accident when they are on the phone?

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Driving: Cell Phones & Attention

  • Yes!
    • Overall, the risk of having accidents while on the phone was 4 times greater than when not using it.
    • Relative risk was similar for drivers of all ages and levels of experience
    • No safety advantage for “hands-free”.
    • Calls close to the time of the accident were particularly dangerous….

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Driving: Cell Phones & Attention

  • Strayer & Johnston (2001)
    • driving simulator study.
    • compared low-difficulty phone tasks (shadowing speech) with high-difficulty tasks (word generation).
    • also looked at unconstrained conversations.
    • measured ability to detect changes in traffic signals in the simulated environment (like the change blindness demos we saw in previous lectures).

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Driving: Cell Phones & Attention

  • Results.
    • talking on phone increased probability of detecting traffic signal change & increased reaction time to change
    • No effect of listening to the radio

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Aviation: Flight Simulation

  • What needs to be in a flight simulator to train pilots effectively?
  • Is a lot of detail always a good thing?
  • From what we have learned we should expect simulator to be “good” if it simulates the visual cues accurately.

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Aviation: Flight Simulation

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  • Gray & Regan (1999)
    • simulated approach to different textured surfaces
      • some with correct expansion of texture elements, others with no expansion
      • measured estimates of TTC

Correct

No exp.

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Aviation: Flight Simulation

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  • Gray & Regan (1999)
    • When texture element expansion is not simulated properly, pilots overestimate TTC
    • I.e., they think they have more time before collision

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Aviation: Flight Simulation

  • Gray & Regan (1999)
    • Implies that it is actually better to have no texture at all than to simulate it inaccurately!
    • What looks good in a static picture may not have the cues needed to perform the action
    • a similar problem now occurs with the process of mipmapping
      • a computer programming algorithm in which texture is distorted to allow for faster processing.

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Aviation: Head-Up Displays (HUD)

  • Pilots have an overwhelming amount of visual information in the cockpit to process!!

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Aviation: Head-Up Displays (HUD)

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  • Assumption: Putting more information in foveal vision will allow pilot to process faster and with less attentional demands
    • extension of artificial horizon indicator

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Aviation: Head-Up Displays (HUD)

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  • Information projected onto a transparent screen behind the windshield or onto the windshield itself
  • Pilot can take in information like altitude and airspeed without having to draw his/her attention away from the outside scene

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Aviation: Head-Up Displays (HUD)

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  • Effect on Attention
    • are the basic assumptions correct?
    • Fischer et. al (1980)
      • simulator study
      • compared ability of pilots to detect an unexpected object (another aircraft) on the runway with an without using the HUD
      • With HUD, pilots often failed to notice object and when it was noticed reaction time was much slower
      • what’s happening?

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Aviation: Head-Up Displays (HUD)

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  • Effect on Attention
    • with HUD, pilot separates information into near and far.
    • focusing on near filters out information from far.
    • pilots are serially processing HUD display and outside world even thought they are superimposed.
    • Same as with normal cockpit, but in that instance pilot is aware than when he/she is attending to instruments he/she can’t see the outside world.
    • Similar to the cell phone problem in driving.

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Next time:

  • Something besides vision!!!
  • The Auditory System
  • Please read: Chapter 9: 205-226

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