Sensitivity to visual features in inattentional blindness

Abstract

The relation between attention, perception and awareness is among the most fundamental problems in the science of the mind. One of the most striking and well-known phenomena bearing on this question is inattentional blindness (IB; Neisser & Becklen, 1975; Mack & Rock, 1998; Most et al., 2001, 2005). In IB, naive observers fail to report clearly visible stimuli when their attention is otherwise engaged--famously even missing a gorilla parading before their eyes (Simons & Chabris, 1999). This phenomenon and the research programs it has motivated carry tremendous theoretical significance, both as crucial evidence that awareness requires attention (Cohen et al., 2012; Prinz, 2012; Noah & Mangun, 2020) and as a key tool in seeking the neural correlates of consciousness (Rees et al., 1999; Pitts et al., 2014; Hutchinson, 2019). However, these and other implications critically rest on a notoriously biased measure: asking participants whether they noticed anything unusual (and interpreting negative answers as reflecting a complete lack of perception). Here, in the largest ever set of IB studies, we show that, as a group, inattentionally blind participants can successfully report the location, color and shape of the stimuli they deny noticing. This residual visual sensitivity shows that perceptual information remains accessible in IB. We further show that subjective reports in IB are conservative, by introducing absent trials where no IB stimulus is presented; this approach allows us to show for the first time that observers collectively show a systematic bias to report not noticing in IB--essentially playing it safe in reporting their sensitivity. This pair of results is consistent with an alternative hypothesis about IB, namely that inattentionally blind subjects retain some degree of awareness of the stimuli they fail to report. Overall, these data provide the strongest evidence to date of significant residual visual sensitivity in IB. They also challenge the use of inattentional blindness to argue that awareness requires attention.