Dissertations, Theses, and Capstone Projects

Date of Degree


Document Type


Degree Name



Cognitive Neuroscience


Tatiana Emmanouil

Committee Members

Robert Duncan

Subject Categories

Cognitive Neuroscience


ensemble, perception, vision, metacognition, online experiment


Ensemble perception is a process that allows our sensory systems to rapidly extract summary information about the stimuli in the environment. For example, we are able to get a sense of the average number of items in a group of similar items (Burr & Ross, 2008; Halberda, Sires, & Feigenson, 2006) or the average size of a group of similar shapes of different sizes (Ariely, 2001). It is theorized that the qualitative result of ensemble perception is that it provides a gist impression of the current environment, which then enables attentional processes in the brain to determine which parts of the environment should next be attended to (Alvarez, 2011). Metacognition is a cognitive process in which thoughts, mental performance, or sensory representations are consciously accessed and analyzed. Because ensemble representations form so rapidly, it is not known whether they can be consciously accessed by metacognitive processes. Here, we explored whether or not ensemble representations can be metacognitively accessed by having participants report the average angle of an array of lines with semi-random angles (a low-level visual ensemble) and then asking them to rate their levels of confidence in their answers. We then calculated the degree of correlation between their performance on the ensemble task and their reported confidence levels, along with some other measures, both at the individual and group levels. Although there were some weak correlations between some of the measures, we did not find that there was any correlation between task performance and confidence.