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Kathleen Vancleef, Jenny Read, William Herbert, Nicola Goodship, Maeve Woodhouse, Ignacio Serrano-Pedraza; Forced-choice disparity detection: are two or four alternatives most efficient in children?. Journal of Vision 2016;16(12):843. doi: 10.1167/16.12.843.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction Measuring accurate thresholds in children can be challenging. A typical psychophysical experiment is usually too long to keep children engaged. However, a reduction in the number of trials decreases the precision of the threshold estimate. We evaluated the efficiency of forced-choice paradigms with 2 or 4 alternatives (2AFC, 4AFC) in a disparity detection experiment. 4AFC paradigms are statistically more efficient, but also more cognitively demanding, which might offset their theoretical advantage in small children. Methods We ran simulations evaluating bias and precision of threshold estimates of 2AFC and 4AFC paradigms. In addition, we measured disparity thresholds in 47 subjects with a 4AFC paradigm and in 75 subjects with a 2AFC paradigm, both using an adaptive weighted one-up one-down staircase (aged 4-61 years). Average threshold estimates as well as bias and precision were compared between both paradigms after 30 and 60 trials. Bias and precision was evaluated by comparing the estimates after 30 or 60 trials with the estimate after 80 trials. Results Simulations indicate a similar bias and precision for a 2AFC paradigm with double the number of trials as a 4AFC paradigm. On average, estimated threshold of the simulated data was equal to the model threshold, indicating no bias. The precision was improved with an increasing number of trials. Likewise, our data showed a similar bias and precision for a 2AFC paradigm with 60 trials as for a 4AFC paradigm with 30 trials (p > .05). Trials in the 4AFC paradigm took slightly longer as participants scanned more alternatives (p < .01). However, 4AFC still ended up faster for a given precision (p < .001). Conclusion Bias and precision are similar in a 4AFC task compared to a 2AFC task with double the number of trials. However, a 4AFC paradigm is more time efficient and is therefore recommended.
Meeting abstract presented at VSS 2016
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