REACTIONTIME LAB PROBLEM: What can change reaction time? Materials: Metric ruler Calculator Procedure: Reaction time is how long it takes for a message to travel along your nerve pathways. 1) Position your left hand over the edge of a table or desk and hold out your thumb and index finger. 2) Have a partner hold a metric ruler just above your hand so the 0 is right above your outstretched thumb and index finger. 3) When your partner drops the ruler, try to catch it between your thumb and index finger as quickly as you can. 4) Record where the top of your thumb is when you catch the ruler. Make your measurements to the nearest 0.5 cm . Put this number in your data table as trial 1. At any time if you do not catch the ruler in time, repeat the experiment. 5) Repeat the procedure four more times. You should have a total of 5 good catch times. 6) State if you think the ruler will fall farther if you catch it with your right hand. 7) Repeat the procedure four times using your right hand to catch the ruler. 8) Switch roles and drop the ruler for your partner. 9) Calculate the average distance the ruler fell for each hand. Be sure to show your work. 10) Convert the cm to m for the average distance fallen. Again, show your work. 11) Use the equation \( d=1 / 2 g t^{2} \) and the average distance fallen to find your reaction time. Remember that \( g=9.8 \mathrm{~m} / \mathrm{s}^{2} \). Again, show ALL of your work and include the units with your answer.

**Factors That Can Change Reaction Time** Reaction time—the interval between the presentation of a stimulus and the individual's response—can be influenced by a variety of factors. Understanding these factors is crucial for interpreting results from experiments like the Reaction Time Lab you've described. Here are some key elements that can alter reaction time: 1. **Age** - **Explanation:** Reaction time generally improves from childhood, peaking in young adulthood, and tends to slow down as people age. This is due to the gradual decline in nerve conduction speed and processing abilities in the brain. 2. **Attention and Focus** - **Explanation:** High levels of concentration can decrease reaction time, allowing for quicker responses to stimuli. Conversely, distractions or divided attention can lengthen reaction times. 3. **Fatigue and Sleep Deprivation** - **Explanation:** Tiredness impairs cognitive and motor functions, leading to slower reaction times. Lack of sleep affects alertness and the body's ability to process information swiftly. 4. **Anticipation and Predictability** - **Explanation:** If an individual can predict when a stimulus will occur, their reaction time can decrease because part of the response is pre-planned. Unexpected stimuli typically result in longer reaction times. 5. **Physical Fitness and Health** - **Explanation:** Regular physical activity can enhance neuromuscular efficiency, thus improving reaction times. Poor health conditions or injuries may impede quick responses. 6. **Stimulant Use** - **Explanation:** Substances like caffeine or nicotine can temporarily enhance alertness and reaction time. Conversely, depressants like alcohol can significantly slow reaction times. 7. **Practice and Familiarity** - **Explanation:** Repeated practice of a task can lead to faster reaction times as the individual becomes more adept at recognizing and responding to specific stimuli. 8. **Sensory Acuity** - **Explanation:** Sharpness of the senses (e.g., vision and hearing) affects how quickly a stimulus is detected and processed. Better sensory perception can lead to quicker reactions. 9. **Environmental Conditions** - **Explanation:** Factors such as lighting, temperature, and noise levels can influence reaction time. For example, poor lighting may delay visual perception, while excessive noise can be distracting. 10. **Mental State and Stress Levels** - **Explanation:** High stress or anxiety can either heighten alertness (reducing reaction time) or cause cognitive overload (increasing reaction time), depending on the individual and context. 11. **Gender Differences** - **Explanation:** Some studies suggest there may be slight differences in reaction times between genders, often influenced by biological and social factors. However, these differences are typically minimal. 12. **Type of Stimulus** - **Explanation:** The nature of the stimulus (e.g., visual vs. auditory) can affect reaction times. Generally, auditory stimuli are processed faster than visual ones, leading to quicker reactions. **Application to the Reaction Time Lab:** In your Reaction Time Lab, several of these factors could influence the results: - **Hand Dominance:** Whether you're using your dominant or non-dominant hand may affect reaction time. - **Practice Effect:** Performing multiple trials can lead to improved reaction times as you become more accustomed to the task. - **Partner Variability:** Differences in alertness or focus between you and your partner dropping the ruler can introduce variability. - **Environmental Factors:** Consistent lighting and minimal distractions are important to ensure that external factors don't skew your results. By considering these factors, you can better design your experiment, control for variables, and interpret your findings with greater accuracy.