The role of executive attention in object substitution masking

What was that object? On the role of identity information in the formation of object files and conscious object perception

Object files are a psychological representation that allows the human brain to keep track of objects, as they move and change across time. The question regarding what information is used to individuate versus update object files has been the focus of considerable scientific debate. Historically, the role of an object's spatiotemporal history was emphasised, whereas more recent work has demonstrated a key contribution from surface features, such as colour. The purpose of the present study was to investigate the role of identity-level information in the formation and individuation of object files, and how it compares to the contribution of featural information. Using a modified spatial repetition-blindness paradigm, across four experiments, there was convergent evidence that surface features contribute to the formation of object files, whereas the role of identity information was at best much smaller and less reliable than the clear contribution from surface features, and the most parsimonious explanation is that it was not present at all.

Perceptual Errors Support the Notion of Masking by Object Substitution

Two experiments examined the effect of object substitution masking (OSM) on the perceptual errors in reporting the orientation of a target. In Experiment 1, a four-dot trailing mask was compared with a simultaneous-noise mask. In Experiment 2, the four-dot and noise masks were factorially varied. Responses were modelled using a mixture regression model and Bayesian inference to deduce whether the relative impacts of OSM on guessing and precision were the same as those of a noise mask, and thus whether the mechanism underpinning OSM is based on increasing noise rather than a substitution process. Across both experiments, OSM was associated with an increased guessing rate when the mask trailed target offset and a reduction in the precision of the target representation (although the latter was less reliable across the two experiments). Importantly, the noise mask also influenced both guessing and precision, but in a different manner, suggesting that OSM is not simply caused by increasing noise. In Experiment 2, the effects of OSM and simultaneous-noise interacted, suggesting the two manipulations involve common mechanisms. Overall results suggest that OSM is often a consequence of a substitution process, but there is evidence that the mask increases noise levels on trials where substitution does not occur.

Temporal trimming: Evidence that common-onset masking shortens perceptual sampling of conscious object representations

Common-onset masking (COM) refers to a methodology where a mask can impair awareness of an object if the mask's offset is delayed relative to the offset of the object. This method has classically been used to understand how discontinuities in visual input lead to the discrete removal of object representations before they reach conscious awareness. However, COM has recently been shown to reduce the precision of conscious object representations (Harrison, Rajsic, & Wilson, Psychonomic Bulletin & Review, 23(1), 180-186, 2016). As a result, Harrison et al. proposed that COM shortens the temporal window for perceptual sampling of an object's representation, an account consistent with interruption-based theories of masking. In the present study we modified the standard COM methodology to assess the impact of a delayed mask offset on the temporal perception of an object's representation. Across two experiments we provide novel evidence that a delayed mask offset can impair temporal perception of a conscious percept, such that it reduces the percept's perceived duration (Experiment 1), and prematurely terminates updating of the percept's dynamic orientation (Experiment 2). We refer to these results as temporal trimming, and suggest that the mechanism responsible for COM operates during the sustained perception of an object.