Reaction Time free essay sample

â€Å"Reaction Time† is the interval of time between the application of a stimulus and the detection of a response and has been thought to differ based upon the effects of modality and warning signals. In the â€Å"Reaction Time† experiment a total of 24 students from the University of Cincinnati participated in an experiment consisting of two sensory modalities, audition and vision, which were combined with two levels of warning signal status. The two levels of warning signal status were signal onset and signal offset. This provided a total of four experimental conditions and is described as a two by two repeated measures design. The independent variables included both modality and warning signals, while the dependent variable was reaction time. From the results of the experiment, significant evidence in differences of reaction time could be related to both modality and reaction. Furthermore, the experiment showed significant evidence that auditory stimuli accompanied with a signal onset provided faster reaction times compared to visual stimuli accompanied without a warning signal. We will write a custom essay sample on Reaction Time or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page The Effects of Warning Signals on Reaction Time to Auditory and Visual Stimuli Reaction Time has been studied for numerous years in efforts to understand the effects modality and warning signals have on a response stimulus. The basis of â€Å"Reaction Time† was to examine and test the effects both warning signals and auditory/visual stimuli have on response time as found in prior research findings. Past research, including that of Woodworth and Schlosberg (1954), Elliot (1968), and Kohfeld (1971) found that different sensory stimuli resulted in different reaction times, while other researchers, including Foley and Dewis (1960), Blackman (1966), and Niemi (1981), examined the effects of foreperiods and expectancy on reaction time. More specifically, â€Å"Reaction Time† was an experiment conducted to specifically examine the discrepancies in time with regards to both auditory and visual stimuli (modality) via the underlying processes organisms experience and to examine the effects warning signals have on time delay. In efforts to understand the relationships between reaction time to auditory and visual stimuli, one must first establish what reaction time is and then examine the processes involved in audition and visual perception. First, reaction time is the interval of time between the application of a stimulus and the detection of a response, in which the response is followed by any reaction to the stimulus. The delay of time reflects the time taken by several mechanisms of the organism to process information. Such mechanisms include components like: sensory encoding, stimulus identification, response selection and response execution. With this kept in mind, a process so complex can be influenced by several factors including: the nature of warning signals that precede the stimulus to be detected, and the sensory modality of stimuli. To provide a clearer picture of what is happening during this process one can envision how this may be demonstrated in real life. First, a person touches hot water streaming from the faucet and the nerve endings from the finger send signals to the cerebellum by means of the spinal cord. Here, the brain interprets the sense of touch as hot and hurting and therefore sends signals via arm muscles to move the arm away. In this example, the reaction time is the difference between the organism touching the hot water and time it took to pull the arm away. The response stimulus, the signal that indicates an organism should respond, is the cerebellum because it is indicating that there is an unpleasant feeling and the arm should move away. Thus, the cerebellum undergoes sensory encoding; it deciphers the signal from the nerves of the finger as a sensory phenomenon (in this case touch). The cerebellum identifies the stimulus as pain (stimulus identification) and selects a response stimulus such as pulling the arm away. At this point in the scenario, the cerebellum makes a response selection that communicates to the muscles to move the arm away. When the arm physically moves, the response execution is occurring. With this kept in mind, it is important to also take note of the different types of reaction time experiments including: simple reaction time and disjunctive reaction time. During simple reaction time a subject must react to the presence of the response stimulus, such as the process that occurred with the hot water streaming from the faucet. Disjunctive reaction time occurs when a subject will have more than one choice of responses to a stimulus. Therefore, a subject must not only react to the response signal, but they must also identify which response is appropriate. In this situation, reaction time delay may be attributed to the process of identifying which response is appropriate. Disjunctive reaction time is used for the purposes of the â€Å"Reaction Time† experiment with the use of modality and warning signals as independent variables. Though the two types of reaction time experiments differ, both simple reaction time and disjunctive reaction time undergo similar processes including: sensory encoding, stimulus identification, response selection and response execution (as described earlier). Each step of the processes is essential as they help explain the lag difference between reaction time and stimulus detection. The difference in reaction time to a stimulus can specifically be attributed to response stimulus modality. Response stimulus modality refers to the type of sensory medium that the signal acts upon, in this case auditory or visual perception. In the previous work of Woodworth and Schlosberg (1954), it was found the auditory stimulus was 40 milliseconds (ms) faster than the visual stimulus with regard to reaction time. The experimenters continued to hypothesize the difference was due to organ structure, in which audition was found to be a mechanical process (allowing for quicker reactions) and vision established as a chemical process, resulting in slower reaction times (Woodworth Schlosberg, 1954). The difference in reaction time was essential as it provided a basic scientific knowledge of the underlying mechanism involved in completing a reaction time modality activity. Elliot (1968) wrote about the studies of simple visual and simple auditory reaction times suggesting that most if not all of the difference in a longer reaction time was attributed to the failure of prior experimenters (like Woodward and Schlosberg) to accurately target the fovea of the eye. More specifically, he argued that if the eye was not fixated on the target, then the stimulus would hit peripheral areas know to yield slower reaction times than does with the fovea area (the fovea is a small depression in the macula lutea of the retina, containing the area of most distinct vision). When the fovea was targeted at 0 degrees of visual arc the delay was reduced to 17 milliseconds, compared to Woodward and Schlosberg 40 ms, due to the increased number of photoreceptors located at the fovea. Elliot also observed that as distances from the fovea increased, reaction time also slowed down (Elliot, 1968). Though Elliot controlled the experiment in regards to peripheral vision and distance, it was still found that differences in modality could continue to account for the differences in reaction time. Kohfeld (1971) however, explained the differences between auditory stimulus reaction time and visual stimulus reaction time as invalid because both stimuli could not be measured on the same scale. He furthermore emphasized that special considerations were needed to be taken when comparing auditory and visual stimuli, in effort to ensure proper measurement validity. Kohfeld argued the intensity of the auditory signal was greater than the intensity of the visual signal when place on the same scale; this scale was measured in decibels. His findings indicated that if the stimulus was presented at less then 30 decibels the difference could be attributed to an unrecognizable stimulation of photoreceptors, however when presented at greater than 30 decibels there was no difference in reaction time for modality (Kohfeld, 1971). Kohfeld contributed to the â€Å"Reaction Time† study as he controlled for the experiment by measuring the two stimuli on the same scale, which was measured in decibels. In this experiment, warning signals were also examined with regards to reaction time involving auditory and visual stimuli. A warning signal is essentially a signal that informs the organism a response stimulus is about to be presented. Furthermore, an optimal preparatory state for the warning signal can be reached, but will only be maintained for a brief period of time. An optimal preparatory state is the duration of time in which a person suspects for a stimulus. Participants can bring about peaks of preparation and respond more quickly as these peaks have more temporal overlap with the auditory response stimulus in comparison to a visual stimulus. A warning signal continues to alert participants that a response signal will occur soon, thus allowing them to prepare to respond. During the preparatory period or foreperiod, the period directly following a warning signal and before a response signal, a participant can undergo a mixed block or pure block set of trials. A mixed block is a set of trials with differentiating timed foreperiods (the exact number and duration of these periods is set by the experimenter). A pure block is a set of trials featuring only one timed foreperiod duration. More specifically, if a mixed block has been set by the experimenter then varying time between the preparatory periods are made before the response signal, whereas a pure block of trials features only one preparatory period or duration before a response signal. Another important spect of mixed block and pure block trials is the critical moment. The critical moment is the possible time needed of a response stimulus relative to the warning signal to sustain optimal preparatory states in a set of trials. In the case of a mixed block, the number of critical moments is equal to the number of foreperiods being used, while a pure block has only one critical moment. Lastly, in the experiment for â€Å"Reaction Time,† imperative moment can also be measured and is the actual time it takes to complete a response in a given trial. Foley and Dewis (1960) examined the relationships between the duration of the foreperiod and the duration of the warning signal in simple reaction time experiments and found that effective foreperiods starting with the onset of a warning signal and a two second effective foreperiod resulted in significantly faster reaction times in comparison to four or eight second foreperiod reaction times without warning signals. Onset of a warning signal indicates to the participant to be ready to respond by its advent. Foley Dewis, 1960). Foley and Dewis’s contributed to â€Å"Reaction Time† experiment as they examined varying times between the preparatory periods and the response signals, not to mention the onset of warning signals. In the experiment conducted by Roger Blackman (1966), it was suggested that the warning signal used in a reaction time experiment may influence two factors, which affect a participant’s readiness to respond and include: temporal uncertainty and expectancy. Temporal uncertainty is the inability of a participant to estimate the moment of presentation of an expected event, or for the purpose of â€Å"Reaction Time† a stimulus. For example, if a participant has to synchronize a response with the onset of a response signal, the variance in response latency increases positively with the foreperiod. Thus, as the foreperiod increases, the time uncertainty will increase. In congruence with the â€Å"Reaction Time† experiment, the increase in time uncertainty is assumed to reduce the participant’s preparatory state at the imperative moment, which in turn prolongs reaction time as well. In the case of pure blocks, time uncertainty is the only factor that determines the variation in the preparatory state, which continues to explain the observed reaction time increase as a function of foreperiod (Blackman, 1966). Another variable affecting a participant’s readiness to respond is expectancy. In mixed blocks, time uncertainty is considered to be controlled by the expectancy of the participant in regards to which of several critical moments is going to be important on a given trial. This assumes that participants in a mixed block will form a belief about when the response signal will occur. The closer the response signal occurs to the time the participant believes it will, the faster the participant’s reaction time will be. Blackman (1966) validated that warning signals help reduce temporal uncertainty, in which reaction time on trials with a warning signal will be faster than trials without warning signals (Blackman, 1966) Like Blackman, Pekka Niemi (1981) was particularly interested in simple visual and auditory reaction processes, with the most emphasis on preparatory periods. He found there were foreperiod variables which affected reaction time and included: duration, regularity, range, distribution, and preceding foreperiods. He also examined factors affecting the relationship between foreperiods and reaction times including: modality, intensity, probability, and duration of the warning signal and reaction stimulus. Through his research a subject’s expectancy is the most important determinant of the preparation to respond to the reaction stimulus at any moment during a trial. Niemi furthermore found that other factors have a direct influence on preparation and include: short-term exhaustion and fatigue and immediate arousal evoked by intense auditory stimuli (Niemi, 1981). Much of what has learned to be the source of difference in reaction time can be attributed to both preceding foreperiods and expectancy. From the works of Woodworth and Schlosberg (1954), Elliot (1968), Kohfeld (1971) on modality, it is predicted auditory signals will be reacted to faster than visual signals in the â€Å"Reaction Time† experiment and that both stimuli will provide significant results in the differences in reaction time. Also, because of findings from Foley (1960), Blackman (1966), and Niemi (1981) on warning signals, it is predicted the presence of a warning signal will cause a faster reaction to the stimulus in comparison to a reaction time in which no warning signal was present. When the two factors are simultaneously combined it is predicted the faster reaction time will occur when a temporal warning signal are present and slower reaction times will result when a visual stimulus is presented without a warning signal. Method Participants A total of 24 students from the University of Cincinnati participated in the research for the experiment â€Å"Reaction Time† with an age range from 19 to 30 and a mean age of 23. Participation was voluntary and students participated from Dr. Warm’s 381 Research Methods class to provide data for the first laboratory report. The data collected was composed from both male and females, where females were numbered under the â€Å"age column† as one and males were numbered under the â€Å"age column† as two (Appendix C). Each participant received 36 trials including nine consecutive trials under each of the following conditions: bar onset/ acoustic signal, bar offset/ acoustic signal, bar onset/ visual signal, and bar offset/ visual signal. Nevertheless, the same 23 students participated in all conditions. All participants were treated in an ethical manner (American Psychological Association, 1992). Experimental Design During the experiment two sensory modalities, audition and vision were combined with two levels of warning signal status. The two levels of warning signal status were signal onset and signal offset. This provided a total of four experimental conditions and is described as a two by two repeated measures design. Apparatus Reaction Time was an experiment conducted via a Pentium IV PC computer using SuperLabs software, in which all stimuli were randomized by means of the Pentium IV PC computer. The computer recorded reaction time in milliseconds (msec). The stimuli involved for the purposes of this experiment include: signal onset, signal offset, audition stimuli and visual stimuli. Preparatory intervals of 2. 1, 2. 4, and 2. 7 seconds were delineated by either the onset or offset of a warning bar located in the center of the screen of the Pentinum IV PC computer (it is 29 mm long). Furthermore, a warning bar onset remained illuminated until subject responded to the signal. Procedure Each participant from this study received 36 trials including nine consecutive trials under each of the following conditions: bar onset/ acoustic signal, bar offset/ acoustic signal, bar onset/ visual signal, and bar offset/ visual signal. Twelve separate condition sequences were randomly assigned to the participants of the study. The 12 condition sequences were as follows: (1234), (1324), (4231), (4321), (2143), (2413), (3142), (3412), (1342), (1432), (2341), (2431), (3124), (3214), (4123), and (4213). Furthermore, the order of preparatory intervals was randomly varied by the computer for each participant; each preparatory interval appears three times within each block of nine trials. Stimuli were given on an average of rate of 1 trial every eight point four seconds, where the maximum stimulus duration was two seconds. Hence the signal to be detected vanished as soon as the participant responded appropriately. Before the actual progression of the experiment, participants were given five practice trials. First place the disc in the disc drive and turn the computer and the monitor on. Now wait for the light on the disk drive to go off and follow the instructions provided by the computer. The computer screen will display a message that says â€Å"PRESS THE SPACE BAR TO GO ON TO THE FIRST CONDITION’S PRACTICE TRIALS,† in which the experimenter can bring in and seat the participant. The experimenter will then proceed to ask the participant which hand is his or her preferred hand (left or right) and read to the participant how to participate in the study via the space bar on the computer and will explain that there will be four portions to the experiment. The experimenter also mentions at the beginning of each portion, the participant will receive five practice trials. If, at any point during the practice, the participant has questions, they are free to ask them. After the participant finishes the practice trials of the experiment, the experimenter will press the space bar to continue and the participant will read instructions for the first part of the experiment. During this portion of the experiment a bar will appear in the center of the screen. The bar is the warning signal indicating to the participant they should prepare to respond. Shortly after the bar has appeared, the participant will hear a tone. Whenever the participant hears the tone, they are to press the space bar as quickly as they can. Now, the experimenter will once again press the space bar to begin the practice trial and the participant is to respond just as they did in the practice trials, the only difference being that all of the trials presented before them will be given a rest and therefore the participants are to continue until they are told to stop. Once the participant finishes this portion of the experiment, the experimenter can press the space bar to continue. Now, the participant will look for a bar on the computer screen which will disappear from the center of the screen soon after. This is the warning signal indicating to the participant to respond. Shortly after the bar has disappeared, the participant will hear a tone. Whenever they hear the tone, they are to press the space bar on the computer as quickly as they can. Once again, the experimenter presses the space bar to begin the practice. During the next portion of the experiment, the participant is to respond just as they did in prior practice trials, except now it is not a practice trial. The experimenter will press the space bar and explain to the participant what they are to do for the third portion of the experiment. During the third portion of the experiment a bar will appear in the center of the screen. This is the warning signal indicating to the participant to prepare to respond. Shortly after the bar has appeared, the participant will see a small black of light appear. The experimenter will press the space bar to begin the practice. Once the practice is over, the participant will take part in the actual experiment just as they did in the practice trials. The experimenter will then press the space bar to continue and will read the following instructions for part four of the experiment. During this portion of the experiment, a bar will appear and then disappear from the center of the screen. This is the warning signal indicating to the participant that they should prepare to respond. Shortly after the bar has disappeared, they will see a small bloc of light appear near the center of the screen. Whenever the participant sees the bar appear, they are to be prepared to respond The experimenter presses the space bar to continue and when the task is completed explains the next part of the experiment. During the next portion of the experiment, the experimenter is to respond just as they did in the practice trials. The only difference now is that it is no longer a practice trial. The experimenter can press the space bar to continue so that the task can be completed by the participant. At the end of the experiment, the computer will read â€Å"END OF EXPERIMENT. PRESS SPACE BAR TO LIST RESULTS. † Now, you can thank the subject for his or her participation and guide them to the nearest exit. In order to recover the results, press the space bar to list the results as instructed by the computer and copy the results exactly as listed. Also label the data sheet accordingly as it appears on the screen. Lastly, to prepare for the next participant, turn the computer off, wait ten seconds, then turn the computer back on and do back to the step that starts out with computer instructions. When finished in the lab, be sure to turn off the computer monitor, clean the lab area and close the door behind you. Results Even more so the experiment closely examines the differences in reaction time between visual and audition stimuli and the onset and offset of warning signals. Early on in the experiment we examine the relationship of reaction time differences in visual and auditory stimuli and found, through the course of the experiment, that auditory stimuli had lower mean score difference in reaction time than visual stimuli. This assumes the notion, established by Woodward and Schlosberg, that audition stimuli had faster reaction times in comparison to visual reaction time. One variable possibly accounting for this difference includes the underlying processes involved for the synthesis of these reactions. More specifically, it was noted by Woodward and Scholsberg (1954) slower reaction times of visual stimuli were attributed to the chemical processes, whereas faster reaction times of auditory stimuli can be attributed to mechanical processes (Woodworth Scholsberg, 1954). The difference in mean reaction time for auditory and visual stimuli is about 19 seconds, which is very close to the difference Elliot (1968) accounted for, which was said to be about 17 seconds. Variances in these times can be accounted for due to the possibility the computer screen was not placed at eye level and therefore, according to Elliot, may have affected the visual arc (Elliot, 1968). Lastly, Kohfeld (1971) contribution to the â€Å"Reaction Time† experiment was essential as he controlled for the experiment by measuring the two stimuli on the same scale (Kohfeld, 1971). Warning signals also significantly impacted the results of reaction time differences, due to the effects of onset and offset of warning signals, expectancy, and duration of foreperiods. For example, the results of the experiment for auditory stimuli paired up with warning signals reflected faster reaction times in comparison to auditory stimuli without warning signals (this was also true for visual stimuli with and without warning signals). According to Foley and Dewis (1960) effective foreperiods starting with the onset of a warning signal resulted in significantly faster reaction times and can be validated as a possible underlying variables in the differences in the lag of time (Foley Dewis, 1960). Furthermore, in the experiment conducted by Roger Blackman (1966), it was suggested that the warning signal used in a reaction time experiment may influence two factors, which affect a participant’s readiness to respond and include: temporal uncertainty and expectancy . More specifically, if the participant tried to synchronize a response with the onset of a response signal, the variance in response latency increased positively with the foreperiod. Thus, as the foreperiod increased so did the time uncertainty (Blackman, 1966). Like Blackman, Pekka Niemi (1981) was particularly interested in simple isual and auditory reaction processes, with the most emphasis on preparatory periods. He found there were foreperiod underlying variables which affected reaction time and included: duration, regularity, range, distribution, and preceding foreperiods. Through his research a participant’s expectancy was the most important determinant of the preparation to respond to the reaction stimulus at any moment during a trial. Niemi furthermore found that other factors have a direct influence on preparation and include: short-term exhaustion and fatigue and immediate arousal evoked by intense auditory stimuli (Neimi, 1981). These variables combined may account for the differences in reaction time for both modality and warning signals. From the experiment, significant evidence provided an interaction of the independent variables (modality and warning signals), in which the faster reaction time included an auditory stimulus paired with the onset of warning signals and the slower reaction times included the visual stimulus paired with the offset of warning signals Though the experiment â€Å"Reaction Time† provided expected results from predictions early on, the delay in time variance may be attributed to systematic and experimental errors in the experiment itself. For example, the computer was placed below eye level and therefore the visual stimuli for reaction time could be delayed due to the lack of optimal perception. Also, if was hard to tell if a person hit the space bar every time, or if they held down the space bar too long during the response. If the person did not actually hit the space bar every time data may be invalid, or if the response was taken after the space bar was held down for a long period of time then data may also be mis-represented. To improve the results for future experiments one might conduct an experiment where the computer was placed at eye level for optimal perception. One may also record the number of times the space bar was actually hit in comparison to the number of recorded signals. Lastly, the experimenter may define the response period as the time the space bar is actually hit versus released.