Recommended tweaks to task instructions

[judithfan]

• "For the warm up trials, you will receive feedback on the correctness, but not on the real trials." --> "For the warmup trials, you will find out whether your response was correct or not, but you won't on the real trials."
• "We expect this study to take approximately 10 to 15 minutes to complete, including the time it takes to read these instructions."