The Effect of Object Size and Speed on Time to Collision Estimation in the Horizontal Plane - PowerPoint PPT Presentation

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The Effect of Object Size and Speed on Time to Collision Estimation in the Horizontal Plane

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The Effect of Object Size and Speed on Time to Collision Estimation in the Horizontal Plane Douna Montazer, Valdeep Saini, Nicole Simone, Danielle Thorpe – PowerPoint PPT presentation

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Title: The Effect of Object Size and Speed on Time to Collision Estimation in the Horizontal Plane


1
The Effect of Object Size and Speed on Time to
Collision Estimation in the Horizontal Plane
  • Douna Montazer,
  • Valdeep Saini,
  • Nicole Simone,
  • Danielle Thorpe

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Initial Research Question
  • Does an objects size have an affect on its
    perception of its speed?

4
Time to Collision (TTC)
  • Time it takes for two objects to collide
  • TTC Estimations persons judgment of time to
    collision
  • Previous research has been dedicated to looming
    objects
  • Object size increases (or decreases) on the retina

5
Background Literature
  • DeLucia and Warren (1994)
  • Looming objects in subjects central field of
    view
  • Results larger objects had smaller TTC
    estimations

6
Background Literature
  • Sidaway et al. (1996)
  • Study involved
  • Results TTC estimates improved with increase in
    the cars velocity

7
Background Literature
  • Marini et al. (2000)
  • Studied whether the final size of the looming
    object affected the accuracy of estimating TTC
  • Results subjects rely on the size difference
    between two stimuli when the objects were
    traveling at a faster speeds
  • However, at the slower speeds the subjects seemed
    to use a mental strategy to judge TTC (Tau)

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Purpose of Current Experiment
  • Test the previous TTC findings within the
    horizontal plane (objects size remains constant
    on the retina)
  • Examine the effects of size on TTC estimations
  • Examine the existing interaction between size and
    speed during TTC estimations

10
Introduction
  • Conditions
  • 3 object sizes
  • 3 speeds
  • 3 disappearance points

11
Cognitive Bias?
  • Generally believed that larger objects tend to
    move slower compared to smaller objects
  • Could be due to a perceived increase in weight,
    or perhaps the amount of effort one would need to
    move a larger object

12
Hypothesis
  • When presented at the same speed, larger objects
    will be perceived to move slower (have longer TTC
    estimations)
  • Subjects should have the best be best at TTC
    estimations for the smallest object at the
    highest speed

13
Questions
  • Design Ideas?

14
Method
  • Subjects
  • 15 subjects - 8 female and 7 male
  • Normal or corrected to normal vision
  • Subjects were naive to the experiment and our
    hypothesis
  • Age range 19-23 years old (M21)

15
Method
  • Apparatus
  • Stimuli created in Microsoft paint and run
    through Presentation software
  • Run on 4 computers

16
Method
  • Object speed (3 levels) 0.204, 0.324, and 0.421
    pixels/msec
  • Object size (3 levels) 1 brick, 5 bricks, 9
    bricks
  • Disappearing points (3 levels) 675, 500, or 325
    pixels from barrier

17
Method
  • 3x3x3 ?a total of 27 possible trial combinations
  • Both background and objects were of the same
    luminance

18
Method
  • Procedure
  • Subjects viewed computer screen at a distance of
    75cm
  • The first block (27 trials) - practice and was
    not included in data analysis

19
Method
  • A fixation cross appeared at the far right side
    of the screen
  • Object appeared and moved towards a stationary
    wall on the opposite side of the screen (left
    side)
  • At one of the disappearance points, both object
    and wall disappeared- screen turned black
  • Subject had to press spacebar when they thought
    the object would have hit the wall, had it not
    disappeared
  • After response, fixation cross reappeared on the
    right side of the screen and the next trial began

20
Demonstration
21
Method
22
Method
  • After every 10 trials, subject was given a 10
    second rest period
  • There were 15 blocks within the experiment (each
    block containing 1 of each 27 trial combinations)
  • Data was analysed using Excel and SPSS

23
Results
  • When presented at the same speed, larger objects
    will be perceived to move slower (have longer TTC
    estimations)
  • Subjects should have the best TTC estimations for
    the smallest object at the highest speed

24
Results
  • 3x3x3 within subjects ANOVA
  • Main effect of Speed
  • F(1.284, 28)23.372, plt0.05

25
Results
  • Graph insert here Speed

26
Results
  • 3x3x3 within subjects ANOVA
  • Main effect of Speed
  • F(1.284, 28)23.372, plt0.05
  • Main effect of Size
  • F(1.821, 28)25.547, plt0.05

27
Results
  • Graph Insert here Size

28
Results
  • 3x3x3 within subjects ANOVA
  • Main effect of Speed
  • F(1.284, 28)23.372, plt0.05
  • Main effect of Size
  • F(1.821, 28)25.547, plt0.05
  • Interaction of Speed and Size
  • F(3.027, 42.379)3.221, p0.032

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Question
  • Improve on our Data Analysis
  • Additional Approaches

38
Discussion
  • Performance declined as both size of the object
    and speed increased
  • Overestimate distance and time regardless of
    speed and size
  • gt accurate for small objects at slow speeds,
  • lt accurate for large objects at fast speeds

39
Discussion
  • Contradicts research
  • ?speed ? ?performance
  • ? speed greater differences between objects
  • Marini, et al.
  • Larger objects produced the least accurate TTC
    estimations at each of the three speeds

40
Discussion
  • WHY?
  • Size
  • Cognitive Bias
  • Changing number of bricks, not just size
  • Stresses importance of cognitive factors

41
Discussion
  • WHY?
  • Speed
  • Working Memory
  • Different Mental Strategies

42
Discussion
  • WHY?
  • Speed x Size Interaction
  • Combination of the previously mentioned
    explanations

43
Discussion
  • Limitations
  • Distance from observer to computer screen
  • SPSS data in pixels
  • Kept distance constant

44
Question
  • What are the implications of this research?

45
Discussion
  • Implications
  • Crossing the street
  • Police using radar guns

46
Question
  • What are some ideas for future research in this
    area?
  • How can you improve upon this research?

47
Discussion
  • Future Research
  • Real-life situations
  • practical/familiar objects
  • Effect of expertise
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