Do we have limited visual capacity? [ongoing]


It is generally understood that individuals have a limited cognitive capacity, hence an appropriate metric of capacity is necessary for the purpose of measuring capacity allocated to represent different forms of information and the final decision itself. Previous research has shown that the sample size model serves as a fitting metric of capacity that characterises capacity precisely and quantifiably. However recent research has reported ambiguous findings - performance in a visual task was better than what the sample size model predicted. Results on the visual task resembled something closer to a capacity-unlimited process rather than a capacity-limited sample-size process. Hence, the present study attempts to make some changes to the visual task and investigate whether the performance is consistent with the sample size model.

Research Questions / Hypotheses

This study attempts to investigate whether the adapted visual stimuli will demonstrate performance consistent with the predictions of the sample size model.


Six participants completed all four sessions and presented complete datasets. 21 participants completed one, two or three sessions but did not complete all four sessions and were excluded.


This experiment is a four session experiment. Each session takes no longer than one hour. The visual task has a pedestal that was an even-colour red circle (Gabor patch). The participants will be presented with either one, two or four offset Gabor patches. They will need to decide whether there was an increment or decrement in the visual stimuli. Since the visual stimuli are offset Gabor patches, an increment is when the centres of the Gabors are shifted slightly upwards while a decrement is when the centres of the Gabors are shifted slightly downwards.


The response accuracy across set size will be modelled against two different computational models. The data will be analysed using the classical likelihood ratio G^2 statistic and AIC to compare model fit. Group data were also fit using hierarchical Bayesian modelling, and model fit was compared using leave-one-out cross-validation.


The findings of our study will contribute to the discussion in the visual working memory literature as to whether visual working memory can be conceptualised by the sample-size model. The results of this study will be communicated in the form of an honours thesis and fourth-year conference presentation.