however , cognitive function tends to 
 decline with age , which can affect the ability to drive safely .
the accident rate per mile 
 driven among drivers over the age of 65 has been found to be higher than that among 
 middle - aged drivers , and when injured in a collision , these older drivers are also more 
 likely to die or to sustain serious injuries2 .
cognitive psychologists have demonstrated that the anterior 
 attention system plays a major role in higher - level executive control of attention during 
 more complex cognitive tasks , such as problem - solving and decision - making , especially when 
 multi - tasking3 .
for example , stephens and tunney5 provided evidence that chewing gum increases scores in 
 immediate , delayed recall , and working memory tests .
similarly , johnson and miles6 confirmed that chewing gum during learning 
 and/or recall improves subsequent memory .
the cognitive processes improved by chewing have 
 been systematically investigated and include memory , attention , and executive function5 . specifically , gum - chewing during cognitive 
 testing has been found to improve verbal working memory and immediate episodic long - term 
 memory , sustained attention and language - based attention .
the results for gum - chewing s 
 effects on word - association executive function are conflicting7 . on the basis of these previous reports
thus , the purpose of 
 this study was to determine the effects of chewing gum on driving performance . to assess 
 this ,
the subjects comprised 26 young drivers ( 10 females ) who held valid driving licenses ( mean 
 driving distance , 87,200  31,134  km / year ; possession of driver s license , 3.40  
 2.20  years ) .
all subjects were informed of the purpose and methods of the study prior to 
 participation and provided their informed consent , following the ethical principles of the 
 declaration of helsinki .
exclusion criteria were ( i ) inability to chew gum for a period of approximately 30  min , ( ii ) 
 age younger than 18 or older than 40  years , ( iii ) consumption of more than 40 units of 
 alcohol per week , ( iv ) smoking more than 10 cigarettes per day , ( v ) currently taking 
 medication , ( vi ) currently experiencing medical problems ( including dental problems ) or 
 serious medical conditions , and ( vii ) allergies to gum6 . a stisim drive m400 driving simulator ( system technology inc . , 

hawthorne , ca , usa ) was used to provide subjects with various driving environments and to 
 estimate their driving performance .
the simulator consists of a car unit with adjustable car 
 seats with a dashboard , a steering wheel , turn signals , and brake and gas pedals , and 
 provides a 135 field of view of a simulated environment .
realistic roadway scenery is 
 projected on a wide computer monitor , placed in front of the center of the steering wheel . 
 speed and gear numbers are displayed on the screen .
auditory feedback is provided through 
 speakers and includes the sound of the engine , braking , speeding around curves , wheels , and 
 driving off the road . before assessment in the simulator , subjects practiced for 5  min .
if a 
 participant demonstrated comfortable performance in the driving trial , he or she was allowed 
 to participate in the test trials .
a 3-day break was provided after each trial : not chewing 
 gum and chewing spearmint sugar - free gum .
the order of the conditions was randomized . in the 
 chewing - gum condition , participants chewed gum at their normal speed ( 1  hz ) during driving . 
 in the control condition ,
the ~30-min 
 driving scenario consisted of a two - lane highway in each direction , with a lane width of 
 3.5  m. subjects were instructed to drive in a steady lateral position in the right ( slower ) 
 traffic lane , following a lead vehicle , while maintaining a steady speed of 80  km / h . 

participants were required to maintain speed limits , comply with traffic rules , and 
 negotiate surrounding traffic .
mean distance driven above the speed limit , lane position , mean distance driven 
 across the center line , and mean distance driven off the road were estimated by the 
 simulator equipment and used as estimates of the driver s abilities of brake , accelerator , 
 and steering control .
differences in driving performance between the no - chewing condition 
 and the chewing gum condition and between genders were assessed using the paired t - test .
the 
 kolmogorov - smirnov test confirmed the data had a normal distribution ; therefore , parametric 
 statistics were used . a p value < 0.05 was considered to indicate 
 statistical significance in all tests .
while chewing gum , drivers drove significantly shorter distances at speeds exceeding the 
 speed limit ( 26.61% shorter ) and off the road ( 31.99% shorter ) than those while not chewing 
 ( p < 0.05 ) .
however , lane position and mean distance driven across the center line did 
 not differ significantly ( p > 0.05 ; table 
 1table 1.effect of gum - chewing on driving capacity ( n=26)chewing gum condition ( mean  sd)no gumchewing gummean distance driven above speed limit ( m)609.9  190.9456.5  166.9lane position ( m)6.79  0.466.81  0.54mean distance driven across center line ( m)59.2  34.343.5  32.9mean distance driven off road ( m)127.0  77.586.4  47.9p < 0.05 ) , and there was no effect of gender in either condition .
safe driving demands the capacity to concentrate and to divide attention over multiple 
 sensory events , including visual and auditory modalities ; it also requires high - level 
 cognitive decisions in a rapidly changing environment8 . in other words ,
driving skills require the simultaneous integration 
 of many types of information while coordinating movements3 .
simulated driving studies indicate that measures of driving 
 behavior , such as speed , lane position , and time / distance across the center line and off the 
 road edge , correlate with a driver s comfort with the given driving conditions .
driving is a 
 complex task requiring appropriate responses to hazardous situations on the road , and 
 research has shown that attention and executive function correlate with driving status .
the 
 stisim driving simulator is widely used to examine the driving abilities of drivers with 
 poor performance9 .
this study assessed 
 mean speed , mean distance driven above the speed limit , lane position , mean distance driven 
 across the center line , and mean distance driven off the road edge as proxies for driving 
 performance . chewing
previous studies have indicated that chewing gum during specific tasks improves 
 reaction times10 and has positive impacts 
 on activities requiring cognitive function .
gum chewing may improve cognitive function by 
 promoting regional cerebral blood flow and glucose delivery and by increasing the efficiency 
 of attention and concentration11 , 12 .
poor performance in a task requiring 
 divided attention is frequently observed in adults with dementia , and previous studies have 
 shown that divided attention problems also exist in many individuals with mild cognitive 
 impairment13 .
cognitively impaired 
 older drivers often do not intend to restrict or stop driving in the future , and do not 
 consider their cognitive problems to be serious ; thus , gum - chewing may reduce the risk of 
 accidents among these individuals while their impairments remain mild3 .
our conclusion is that chewing gum enhances alertness and 
 attention while driving , because it makes drivers feel more comfortable during driving 
 activities .
also , this study has provided further evidence that driving simulators can be 
 used to assess responses to road hazards in a safe environment . driving simulator recordings 
 have previously been used to assess age - related changes in driving performance and 
 cognition14 , and to predict potential 
 future crashes by older drivers15 . 

further research may clarify the mechanism by which chewing gum improves performance in a 
 task , such as driving , that requires sustained attention and executive function .
 [ purpose ] the purpose of this study was to determine the effects of chewing gum on 
 driving performance in a driving simulator . 
 [ subjects ] in total , 26 young licensed drivers 
 participated . 
 [ methods ] the driving scenario was typical of an urban environment : a 
 single - carriageway , two - way road consisting of a mix of curved and straight sections , with 
 considerable levels of traffic , pedestrians , and parked cars . 
 mean distance driven above 
 the speed limit , lane position , mean distance driven across the center line , and mean 
 distance driven off the road were used as estimates of brake , accelerator , and steering 
 control . 
 the results were compared with those of a non - chewing gum control condition . 
 [ results ] the driving performance while chewing gum was significantly better : the mean 
 distance driven above the speed limit was 26.61% shorter , and 
 the mean distance driven off 
 the road was 31.99% shorter . 
 lane position and mean distance driven across the center line 
 did not differ significantly between the two conditions . 
 [ conclusion ] chewing gum appears 
 to enhance driving performance during a sustained attention driving task . 