{"pk":28723,"title":"Selectivity metrics provide misleading estimates of the selectivity of single units inneural networks","subtitle":null,"abstract":"To understand the representations learned by neural networks(NNs), various methods of measuring unit selectivity havebeen developed. Here we undertake a comparison of four suchmeasures on AlexNet: localist selectivity (Bowers et al., 2014);precision (Zhou et al., 2015); class-conditional mean activityselectivity CCMAS (Morcos et al., 2018); and top-class se-lectivity. In contrast with previous work on recurrent neuralnetworks (RNNs), we fail to find any 100% selective ‘local-ist units’ in AlexNet, and demonstrate that the precision andCCMAS measures are misleading and suggest a much higherlevel of selectivity than is warranted. We also generated ac-tivation maximization (AM) images that maximally activatedindividual units and found that under (5%) of units in fc6 andconv5 produced interpretable images of objects, whereas fc8produced over 50% interpretable images. Furthermore, theinterpretable images in the hidden layers were not associatedwith highly selective units. We also consider why localist rep-resentations are learned in RNNs and not AlexNet.","language":"eng","license":{"name":"","short_name":"","text":null,"url":""},"keywords":[{"word":"localist representation; grandmother cells; dis-tributed representations."}],"section":"Papers with Poster Presentations","is_remote":true,"remote_url":"https://escholarship.org/uc/item/6p15m57n","frozenauthors":[{"first_name":"Ella","middle_name":"M.","last_name":"Gale","name_suffix":"","institution":"University of Bristol","department":""},{"first_name":"Ryan","middle_name":"","last_name":"Blything","name_suffix":"","institution":"University of Bristol","department":""},{"first_name":"Nicholas","middle_name":"","last_name":"Martin","name_suffix":"","institution":"University of Bristol","department":""},{"first_name":"Jeffrey","middle_name":"S.","last_name":"Bowers","name_suffix":"","institution":"University of Bristol","department":""},{"first_name":"Anh","middle_name":"","last_name":"Nguyen","name_suffix":"","institution":"Auburn University","department":""}],"date_submitted":null,"date_accepted":null,"date_published":"2019-01-01T18:00:00Z","render_galley":null,"galleys":[{"label":"PDF","type":"pdf","path":"https://journalpub.escholarship.org/cognitivesciencesociety/article/28723/galley/18594/download/"}]}