ATTENTIONAL ENGAGEMENT SELECTIVELY MODULATES EPISODIC ENCODING

Yes/No (YN) detection and two-alternative forced-choice (2AFC) tasks have been used to investigate the relationship between perceptual sensitivity and visual awareness (Weiskrantz, 2009; Balsdon & Azzopardi, 2015). It was found that a blindsight patient performed worse on the YN task than 2AFC, to a degree that was beyond theoretical expectation (Azzopardi & Cowey, 1997, 1998). Similarly, in recognition memory research, YN has been used to assess episodic memory, yet findings comparing YN and 2AFC performance remain mixed in some patient studies (Aggleton & Shaw, 1996; Bayley et al., 2008).

We investigated whether attentional engagement selectively modulates performance of YN and 2AFC tasks. For this, we measured how much an individual’s eye-gaze pattern synchronized to the average responses by other subjects, during encoding. Thirty participants watched four 20-minute movies, followed by a combined YN–2AFC task. On each trial, participants first judged whether an image had appeared in the movie (YN), followed by a 2AFC decision between this same stimulus and an additional target/foil (to identify the target).

The degree to which an individual’s gaze pattern correlated with other subjects’ average responses during encoding positively predicted YN accuracy but not 2AFC accuracy. This effect was driven by hits (correct identification of targets) but not correct rejections of foils. This suggests that attentional engagement during encoding may enhance subsequent episodic recall, selectively benefiting the subsequent recognition of targets. In 2AFC such enhancement may be less critical because performance could rely on comparing the (non-episodic) familiarity signals between the two stimuli.