David Strayer Department of Psychology

1. Multi-tasking on the Information Super Highway: Why Using a Cell Phone Can Make You Drive Like You’re Drunk David Strayer Department of Psychology RMPA: April 13, 2007

2. Research Questions • Does conversing on a cell phone interfere with driving? • What are the sources of the interference? • Peripheral interference (dialing, holding the phone) • Attentional interference (cell phone conversation) • How significant is the interference?

3. Observational Study(Residential 4-way Intersections) • Odds ratio for failing to stop: • 0.27 for drivers not using a cell phone • 2.93 for drivers using a cell phone

4. Epidemiological Studies(Case Crossover Design) • Redelmeier & Tibshirani (1997) NEJM • 699 driver involved in a non-injury automobile accident • 4-fold increase in risk of accident when using cell phone • McEvoy et al., (2005) BMJ • 456 drivers requiring hospital attendance after automobile accident • 4-fold increased likelihood of crashing when using a cell phone

5. Driving Simulator Studies(Car Following Paradigm) • Drivers conversing on a cell phone were 5 times more likely to be involved in a traffic accident

6. High-Fidelity Driving Simulator

7. Simulator-Based Studies • Car-following paradigm • Follow periodically braking pace car • Required timely and appropriate reactions • Hands-free cell phone (positioned in advance) • Conditions • Single vs. dual-task • Low vs. moderate density * • Measures • Reaction time • Following distance • Rear-end collisions Single Dual Low Mod.

8. Reaction Time

9. Following Distance

10. Rear-end Collisions

11. Summary (Experiment 1) • Cell-phone driver’s • Slower reaction times • Drivers compensate by increasing following distance • Increase in rear-end accidents • Cell-phone interference • Even when manual contributions are eliminated • Naturalistic conversations

12. Why Do Cell Phones Cause Interference? • From earlier studies, no interference from: • Radio broadcasts (audio input) • Books on tape & recorded conversations (audio/verbal input) • Simple shadowing (audio/verbal input, verbal output) • Implies active engagement in conversation necessary • Impairments from both hand-held and hands-free units • Implies central / cognitive locus • Inattention-blindness (James, Neisser, Simons)

13. Why Do Cell Phones Cause Interference? • From earlier studies, no interference from: • Radio broadcasts (audio input) • Books on tape & recorded conversations (audio/verbal input) • Simple shadowing (audio/verbal input, verbal output) • Implies active engagement in conversation necessary • Impairments from both hand-held and hands-free units • Implies central / cognitive locus • Inattention-blindness (James, Neisser, Simons)

14. Why Do Cell Phones Cause Interference? • From earlier studies, no interference from: • Radio broadcasts (audio input) • Books on tape & recorded conversations (audio/verbal input) • Simple shadowing (audio/verbal input, verbal output) • Implies active engagement in conversation necessary • Impairments from both hand-held and hands-free units • Implies central / cognitive locus • Inattention-blindness (James, Neisser, Simons)

15. Experiment 2: Inattention-Blindness • Test for evidence of cell-phone induced inattention blindness • High-fidelity driving simulator • Hands-free cell phone • Naturalistic conversation with confederate • Eye tracker • Two phases to the study: • Phase 1: Single & dual-task driving • Phase 2: Recognition memory tests for objects encountered while driving

16. Recognition Memory

17. Recognition Memory Given Fixation

18. Experiment 2a: Summary • 50% drop in recognition memory from single to dual-task, consistent with inattention blindness interpretation • What about items more relevant to safe driving? • Do drivers divert attention from processing items of low task relevance (e.g., billboards), but protect high task relevance items (e.g., pedestrians)?

19. Experiment 2b: Effects of Traffic Relevance • Phase I: Single & dual-task driving • Interstate driving (with traffic) • Hands-free cell phone, naturalistic conversations • Unique items placed in single & dual-task scenarios • Phase II: Surprise 2AFC recognition memory test • Single-task items (driving only) • Dual-task items (driving & phone) • Control items (not seen while driving)

20. Driving Safety Relevance Ratings

21. 2AFC Recognition Memory Given Fixation(Corrected for Guessing) Dual-task interference not modulated by driving safety relevance

22. Experiment 2: Summary • Cell phone conversations create inattention blindness for traffic related events/scenes • Cell phone drivers look but fail to see up to half of the information in the driving environment • No evidence that cell phone drivers protect more traffic relevant information

23. Experiment 3: Encoding or Retrieval Deficits? • Encoding deficits • Reduced attention to perceptual inputs • Clear implications for traffic safety • Retrieval deficits • Failure to retrieve prior episodes • Less clear implications for traffic safety • Event-related brain potentials recorded to traffic brake lights • Single-task • Dual-task

24. Traffic-related Brain Activity

25. Experiment 3: Summary • Brain waves suppressed by cell phone conversations • Cell phone conversations impair encoding of information necessary for the safe operation of a motor vehicle

27. Cell Phone vs. Passenger Conversations • Conditions • Single task / dual task • Conversing on cell phone • Conversing with passenger • Design • Task (2) x Condition (2) Single task Passenger Cell

28. Lane Keeping Errors

29. Successful Navigation

30. Traffic References

31. Summary (Experiment 4) • Cell-phone conversations • More navigation errors • Fewer references to traffic • Passenger conversations • Collaborative problem solving • Shared situation awareness • Passenger actively supports the driver

32. Experiment 5: How Significant is the Interference? • Cell-phone vs. drunk-driver • Redelmeier and Tibshirani (1997) reported epidemiological evidence suggesting that “the relative risk [of being in a traffic accident while using a cell-phone] is similar to the hazard associated with driving with a blood alcohol level at the legal limit” (p. 465).

33. Cell-phone Driver vs. Drunk Driver • Car-following paradigm • Follow periodically braking pace car • Required timely and appropriate reactions • Conditions • Single-task driving • Cell-phone driving * • Intoxicated driving (BAC= 0.08 wt/vol) • * Hands-free = Hand-held

34. Reaction Time

35. Following Distance

36. Rear-end Collisions

37. Summary (Experiment 5) • Compared to drunk driver, cell-phone driver’s reactions • Slower reaction times • Longer to recover lost speed following braking • Drivers compensate by increasing following distance • Increase in rear-end accidents • When controlling for time on task and driving conditions, cell-phone drivers’ performance is worse than that of the drunk driver

38. You Cannot Practice Away The InterferenceCooper & Strayer et al., (2007) HFES Accident Frequency for City and Highway Driving

39. Teen Drivers More at RiskChisholm et al., (2006) HFES Accident Percentage – pedestrian and pullout vehicle events

40. Research Questions • Does conversing on a cell phone interfere with driving? • Yes • What are the sources of the interference? • Peripheral interference (dialing, text messaging) • Attentional interference (inattention blindness) • How significant is the interference? • Worse than listening to radio/books on tape • Worse than in-vehicle conversations • More impairing than driving while intoxicated at legal limit