The effect of multiple responses and certainty estimates on the integration of visual information

Integration of information was investigated in two experiments that employed a multiple-observation, tilt-discrimination task. The integration model of signal-detection theory generally overestimated the improvement in discrimination resulting front additional observations. Further, probabilistic multiple responses appeared detrimental to discrimination. These results differ from earlier findings using different discrimination tasks. Reasons for the differences were discussed in terms of within-trial redundance and interference caused by complex response modes.