The analyses were limited to participants who completed the simulator drive or whose drive was not interrupted. Preliminary analyses indicated that gender did not interact with cell-phone usage to affect any of the performance or assessment measures in the study. Consequently, gender was not included in the reported analyses.
Driving errors and driving safeness
The most basic measure of the actual safeness of participants’ driving on the simulator was the total number of errors they made. In order to distinguish the severity of the errors and create more detailed measures of driving safeness, we asked a different group of 69 respondents to indicate the seriousness of each of the driving errors or violations on a 6-point scale anchored by “0” = not at all serious and “5” = highly serious. The mean rating of each of the driving errors is presented in Table 1. There were two errors (failing to signal and speeding) that were perceived to be less severe than the others. When the errors were ordered in terms of judged severity, the only significant pair-wise contrast between an error and the next most serious error was between the errors of speeding and making an illegal turn, t(68) = 2.17, p = .033, d = .53. Consequently, failing to signal and speeding were labeled as “minor” errors while the remaining ten were labeled as “serious” errors. The minor errors have face validity as being less severe in that they are less likely to directly lead to an accident than more serious errors such as failing to yield to a vehicle with the right of way. Distinguishing the minor errors from the serious errors was important, because it was anticipated that the serious errors would be the primary basis for participants’ assessments of the safeness of their driving and their confidence in their ability to drive safely while distracted.
Table 2 presents the serious and minor driving errors made in the cell-phone and control groups. A comparison of the errors in the two groups revealed that cell-phone participants made significantly more serious errors t(98) = 2.72, p = .008, d = .55, but not more minor errors, t(98) = .68, p > .250, d = .14, than control participants.
Participants’ assessments of the safeness of their driving and their estimations of the number of driving errors they made in the cell-phone and control groups are also presented in Table 2. Cell-phone participants were expected to perceive their driving to be less safe and to report they made more errors because of the widespread expectation that cell phones impair driving performance. Somewhat surprisingly, cell-phone participants did not remember making more serious errors, t(98) = .67, p > .250, d = .13, or more minor errors than control participants, t(98) = 1.33, p = .185, d = .27. However, as anticipated, cell-phone participants perceived that they drove less safely than control participants, t(98) = 4.97, p = .001, d = .99. The groups also did not differ in terms of their perceptions of their general ability to dive safely while distracted following the simulator session, t(98) = 1.67, p = .097, d = .34.
Relation between perceived and actual driving safeness
Analyses were performed to examine whether participants’ assessments of the safeness of their driving were based on awareness of the actual safeness of their driving (see Table 3). Control participants’ assessments of their driving safety were negatively correlated with their serious driving errors, r(49) = −.37, and uncorrelated with their minor driving errors. Thus, control participants’ assessments of the safeness of their driving decreased as the number of serious driving errors they made increased. By contrast, cell-phone participants’ assessments of their driving safety tended to be positively correlated with their serious driving errors, r(49) = .25, and uncorrelated with their minor driving errors. A comparison of these correlations revealed that self-assessments of driving safety were more accurate and better correlated with the actual driving errors in the control group than the cell-phone group, F(1,96) = 10.25, p = .002, η2 = .10. That is, cell-phone participants were less aware of the actual safeness of their driving than control participants.
Further evidence of cell-phone participants’ lack of driving self-awareness comes from an analysis of their memory of their driving errors. Control participants’ memory of their serious driving errors was positively correlated with their actual serious driving errors, r(49) = .40, but their memory of their minor driving errors was not correlated with their actual minor driving errors. The pattern suggests that control participants were cognizant of the serious errors they were making. In contrast, cell-phone participants’ memory of their serious driving errors was not correlated with the actual number of serious errors they made, r(49) = .05. However, a comparison of the correlations found that the memory for serious driving errors did not significantly differ between cell-phone and control groups, F(1,96) = 3.20, p = .077, η2 = .03.
Predictors of confidence in driving ability
The final set of analyses focused on the predictors of participants’ general confidence in their ability to drive safely while distracted. From Table 3 it is apparent that both control and cell-phone participants’ confidence in their ability to drive safety while distracted was negatively correlated with their perceived serious driving errors. However, only control participants’ confidence in their ability to drive safely while distracted was grounded in the actual safeness of their driving. The confidence of control participants was negatively correlated with their serious driving errors, r(49) = −.32, whereas the confidence of cell-phone participants was uncorrelated with their serious driving errors, r(49) = .13. The control and cell-phone groups differed in the relationship between the assessments of their ability to drive safely while distracted and their serious driving errors, F(1,96) = 5.04, p = .027, η2 = .05.