Among the participants from China, white tablets were seen as having the greatest efficacy in treating headaches. Diamond-shaped tablets had high expected difficulty in swallowing and were seen as most alerting. The least bitter tablets were oval-shaped but also were least effective for treating headaches. Circular-shaped tablets were easiest to swallow and most effective for headache. For colors, red and blue tablets were expected to be hardest to swallow, red and green tablets more bitter, red tablets most alerting, and white tablets most effective in treating headaches.

The Colombian participants viewed pink and white tablets as tasting less bitter than the other colors; oval-shaped tablets were the least bitter and least effective for headache, while diamond-shaped tablets were hardest to swallow. Red tablets were seen as the most alerting and white tablets were expected to be most effective at treating symptoms of headache.

Lastly, the U.S. group viewed yellow and white tablets as less bitter, red and orange as more alerting, and white tablets as most effective in treating headache. Diamond-shaped tablets were the most difficult to swallow and oval-shaped ones were the least bitter, least effective, and most alerting. For shape, circular tablets were easiest to swallow and most effective in treating headaches. No significant differences were seen between results of the red and light-red, blue and light-blue, or green and light-green findings in any of the groups.

The cultural variations observed in the results suggest that there is no one color or shape that is optimal for pills in general. If patients have poor medication adherence based on complaints of difficulty of swallowing or taste, clinicians should also examine the shape and color of the drug for potential biases.

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