View from the top: Hierarchies and reverse hierarchies in the visual system

Shaul Hochstein*, Merav Ahissar

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

1051 Scopus citations


We propose that explicit vision advances in reverse hierarchical direction, as shown for perceptual learning. Processing along the feedforward hierarchy of areas, leading to increasingly complex representations, is automatic and implicit, while conscious perception begins at the hierarchy's top, gradually returning downward as needed. Thus, our initial conscious percept - vision at a glance - matches a high-level, generalized, categorical scene interpretation, identifying "forest before trees." For later vision with scrutiny, reverse hierarchy routines focus attention to specific, active, low-level units, incorporating into conscious perception detailed information available there. Reverse Hierarchy Theory dissociates between early explicit perception and implicit low-level vision, explaining a variety of phenomena. Feature search "pop-out" is attributed to high areas, where large receptive fields underlie spread attention detecting categorical differences. Search for conjunctions or fine discriminations depends on reentry to low-level specific receptive fields using serial focused attention, consistent with recently reported primary visual cortex effects.

Original languageAmerican English
Pages (from-to)791-804
Number of pages14
Issue number5
StatePublished - 5 Dec 2002

Bibliographical note

Funding Information:
Special thanks to Orit Elgavi-Hershler for permission to cite unpublished results. We thank Anne Treisman, Robert Shapley, Peter Hillman, Howard Hock, Vince Di Lollo, Ehud Ahissar, and Ehud Zohary for fruitful discussions of this study. This work was supported by grants from the Israel Science Foundation of the Israel Academy of Sciences and Humanities (“Center of Excellence” grant #8009) and the US-Israel Bi-National Science Foundation (BSF).


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