The episodic nature of consciousness: an investigation using rapid serial visual presentation

Avilés, Alberto (2024). The episodic nature of consciousness: an investigation using rapid serial visual presentation. University of Birmingham. Ph.D.

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Abstract

What is consciousness for? Which cognitive functions can only be carried out with consciousness? Although much empirical work has explored these questions there is still not a definitive answer. In this thesis, we review how the evidence obtained with the Rapid Serial Visual Presentation(RSVP) paradigm could shed light on this issue. A key finding is the low recognition performance for RSVP stimuli that contrasts with the excellent performance in detection and identification tasks. This is suggestive of mechanisms that are highly efficient in the absence of conscious reports. Based on this effect and some of the theoretical ideas accounting for key RSVP effects we hypothesize that one cognitive mechanism that can only be carried out with consciousness is episodic encoding.

The thesis presents a series of experiment testing this hypothesis. Classic episodic memory effects are explored in the context of RSVP experiments. We address the repetition effect, the expected improvement in memory consolidation as items are repeated. Recency effects are investigated in the contexts of recognition and free-recall tasks. Proactive interference and list-length effect are also addressed using RSVP stimuli. Finally, we tested the reportability of task-irrelevant items.

Our main aim is to provide a comprehensive picture of the episodic memory effects that can be observed in RSVP. The results show that many of our findings are consistent with the view that most of the stimuli presented in RSVP sequences are not episodically encoded. This challenges the possibility of unconscious episodic encoding and agrees with our main hypothesis. These findings are discussed in the context of a theoretical proposal about the function of consciousness. The Tokenized Percept Hypothesis suggests that the unconscious activation of categorical or featural information might be enough for processes, such as detection or identification. While the acquisition of episodic properties necessitates conscious processing.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):