Drinking and Driving: How Perception isAltered

Ugochi Onyejiaka

A research paper for PSY 440 (Perception)
Stephen F. Austin State University

What is the first bad thing you think of when you think ofdrinking? It is probably drinking and driving. This is because wehave some knowledge of the amount of accidents that are alcoholrelated. There are approximately one million people injured inalcohol- related traffic crashes annually (PBS, 2002). PBS alsostates that visual impairment caused by alcohol is the singlegreatest factor in motor vehicle deaths and injuries. We see thecommercials that tell us what the consequences are for getting a DWI(drinking while intoxicated) or DUI (drinking under the influence),but what is a person that is intoxicated perceiving and why doeshe/she think it is ok to drive?

First, we would have to define what is alcohol intoxication? Itreally just depends on what state you happen to be in and it seems tofluctuate between .08-.10% blood alcohol level with most stateshaving a .10% blood alcohol level (National Commission Against DrunkDriving, 2003). What we do know is that it affects a person'sperception of everything. When a person ingest the alcohol itcirculates through the persons system and then enters the bloodsystem (Info please, 2002). Once the alcohol is in the blood system,it acts as depressant in the central nervous system. This, in turn,affects neurotransmitter, glutamate, and serotonin. Lookingspecifically at perception, past research has observed howintoxication affects visual contrast sensitivity for stationary andmoving objects, our reaction time, anticipation time, depthperception, and far and near vision.

Let's start by observing what happens to your perception andbehavior in a controlled, nonmoving environment. Nicholson, Wang,Airhihenbuwa, Mahoney, Christina, and Maney (1992) wanted to know ifthe amount of alcohol affected a person's perception differently. The researchers looked at participants' reaction time, anticipationtime, depth perception, and far and near vision after drinking asingle shot drink and a double shot drink. The researchers thencompared the results to each individual's baseline of all of thevariables. However, Nicholson et al. did find that there was asignificant difference in depth perception before alcohol and afteralcohol had been ingested. However, there was only significance whenthe participants' blood alcohol level was on its way to peaking andnot afterwards. This is why when a person has been drinking and thenstops drinking for a long period of time before driving is able topass drinking and driving tests. The person has already peaked and ison there way back down to their baseline and his/her perception isgetting better while it is dropping. Overall, there was decreasedperformance for reaction time, depth perception, and anticipationtime. These are three important factors that we use when driving andthis is impaired significantly by having one or two drinkscasually.

So imagine now a person is drinking and driving and objects aremoving while others are stationary. Nicholson, Andre, Tyrrell, Wang,and Leibowitz (1994) observed how alcohol would interact with thesevariables. Subjects participated in low alcohol, moderate alcohol, aplacebo, or no drink at all double sessions. Participants in themoderate alcohol session had a mean blood alcohol level of .043% andparticipants in the low alcohol session had a mean blood alcohollevel of .011%. They were then exposed to either stationary orcircular moving electronically produced sine waves that randomlychanged speed and spatial frequency. With the circular movingtargets, the participants would be forced to try and make a smoothpursuit eye movement. Results showed that there was a significantloss in contrast sensitivity, and that is was worsened the higher thespatial frequency went. There was also a significant correlationbetween stationary and moving targets. Therefore, if a person hadloss of contrast sensitivity with stationary targets, he/she also hada loss with moving targets. An important finding is that there was asignificant impairment in vision with the blood alcohol level beingaround .043% which is half of what most states prohibit, so imaginehow a person's perception is that has had a couple of drinks?Overall, a person should never drink and drive because a person'sdepth perception and awareness of stationary and moving targets isaltered with just a moderate amount of alcohol.

So now a person decides that he/she is going to take the risk anddrive after drinking. What happens when a police officer pulls over aperson for drinking and driving? Do the tests they give to show aperson's intoxication level actually work or can a person beat it? Atest that most police officers use is the saccadic test. This is whenthe police officer makes a person follow an object (example: a fingeror pen) and the officer is looking for a smooth pursuit of eyemovement. There are actually two methods of using the saccadic test.The first method is to fixate on an object and then slowly move it tothe periphery and then back the opposite way. The second method, thegap method, is to have a person fixate on an object, make the objectdisappear for approximately 200ms, and then have the object reappearin the periphery. This method (the gap method) should result in areduction in saccadic reaction time. This is probably because of thedisconnection of the attention and ocular system from the previouslocation (Tam and Stelmach, 1993). Wegner and Fahle (1999) observedthe effects of the gap effect and predictable targets on sober andintoxicated participants. The same participants were used for boththe sober and intoxicated sessions. The participants' blood alcohollevel ranged from .08-.13% once intoxicated. The researchers observedlatencies for sober and intoxicated participants using both methodsof the saccadic testing and using predictable and unpredictabletargets (ex: small, circular, red dot). Wegner and Fahle found thatparticipants that were intoxicated had significantly higher saccadicreaction times in first method of saccadic testing. They also found asignificant interaction between intoxicated participants and the gapmethod. This means that the intoxicated participants' reaction timewas significantly faster with the gap method. This is probably whypolice officers do not use this method of testing. Police officersobviously use the first method because it is more dependable to testsee if a person is intoxicated.

Overall, alcohol affects a person's perception while driving invarious ways. It decreases clearness of vision by reducing vision bymore than half and side vision is reduced by approximately thirtypercent (Tennessee Drivers Handbook, 2003). The Tennessee DriverHandbook also states how the eye muscles become relaxed and the eyemuscles relaxing could lead to poor glare vision. All of thesefactors that impair vision increase the chances of head on andrear-end collisions.

From the previous studies, it seems as though most of theresearchers are observing moderately intoxicated people. They arefinding that a small amount of alcohol can affect a person's depthperception, contrast sensitivity, and saccadic eye movement. It isno wonder that a person's depth perception is altered. Humans havetwo frontal, parallel eyes that are binocular. Therefore, we can seesimultaneously from both eyes. This occurs because each eye has afixed visual angle of 104 degrees and part of each eye's anglesoverlap (Info quest, 2003). The overlap allows our brains toperceive relative depth information. When any alcohol is in oursystem, it runs in our blood stream into the brain and affects motorcontrol and coordination. The result is double vision (diplopicvision).

Alcohol affects everyone differently and I also think that peopleuse it differently. It makes sense to me that younger adults abusealcohol more than older adults and when researchers are conductingexperiments they are using participants that are older than collegeaged students. This is great, but I think that research needs toexplore how alcohol intoxication affects perception with participantsthat are having more than just one or two drinks and are closer tothe average college age (18-22). This is because drinking usuallystarts at the high school age or at least a college-aged person andthis is when I believe alcohol habits form. According to a pollconducted by PBS (2002), of the 20 million high school juniors andseniors they polled, almost half reported drinking on a monthlybasis. Future research seems to be leaning towards observing if agehas any correlation to drinking and driving. Hingson, Heeren,Zakocs, Winter, and Wechler (2003) observed whether college agedstudents who started drinking at a younger age were more prone tobecome frequent drinkers, drive while intoxicated, and ride with aperson that has been drinking. The researchers administeredquestionnaires to college students all across the United States.Their results showed that college students that started drinkingbefore the age of 19 were significantly more likely to be alcoholdependent and heavy drinkers, drive after drinking, ride with friendsthat have been drinking, and acquire some kind of injury that neededmedical attention. This suggests that drinking becomes more of asocial norm to people that have been drinking since before the age of19. Also, the consequences of drinking and driving may not botherthem as much as it does students that waited to start drinking. Overall, most accidents happen with young drivers (PBS, 2002) andhaving them drunk behind the wheel is a cause for concern.

In conclusion, drinking and driving is bad whether a person hashad one drink or has been binge drinking. It is bad because italters a person's perception in many ways. One way is by the brainnot combining the information from both eyes, which results indiplopic vision. This also causes inaccurate depth perception. Contrast sensitivity to stationary and moving targets, reaction time,and anticipation time are also altered. Even though most of theparticipants that were used in the previous research range in agefrom 25-30, college age participants and younger should be usedbecause they are the cause of most accidents and if they develop analcohol habit at around this time frame, they are more likely todrive while intoxicated.



Hingson, R., Heeren, T., Zakocs, R., Winter M., & Wechsler H.(2003).Age of first intoxication, heavy drinking, driving afterdrinking, and risk of unintentional injury among U.S. collegestudents. Journal of Studies on Alcohol, 64, 23-91.

Info Quest. (2003). Physiology: Binocular Eyes. Retrieved November21, 2003 from Website: http://library.thinkquest.org/28030/physio/stereo.htm

Info Please. (2002). Physical Effects of Alcohol. RetrievedNovember 20, 2003 from Web site: http://inforplease.lycos.com/ce6/sci/A0856547.html.

National Commission Against Drunk Driving. (2003). State BloodAlcohol Levels Retrieved November 18, 2003 from Web Site:http://www.ncadd.com..

Nicholson, M., Andre, J., Tyrrell, R., Wang, M., & Leibowitz.(1994). Effects of moderate dose alcohol on visual contrastsensitivity for stationary and moving targets. Journal of Studies onAlcohol, 56, 261-266.

Nicholson, M., Wang, M., Airhihenbuwa, C., Mahony, B., Christina,R., & Maney, D. (1992). Variability in behavioral impairmentinvolved in the rising and falling BAC curve. Journal of Studies onAlcohol, 53, 349-356.

PBS. (2002). Drinking and Driving Facts. Retrieved November 17,2003 from Web site: http://www.pbs.org/justone/justo0.htm.

Tennessee Drivers Handbook. (2003). Chapter 5: Safety. RetrievedNovember 17, 2003 from Web site:http://www.state.tn.us/safety/graphics/chap5.pdf.

Tam, W., & Stelmach, L. (1993). Viewing behavior: Ocular andattentional disengagement. Perception Psychophysiology, 54, 211-222.

Wegner, A., & Fahle, M. (1999). Alcohol and visually guidedsaccades: Gap effect and predictability of target location.Psychopharmacology, 146, 24-32.

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