Reuniting Categories, Language, and Perception

Reuniting Categories, Language, and Perception Gary Lupyan (glupyan@cnbc.cmu.edu) Department of Psychology, Carnegie Mellon University Center for the Neural Basis of Cognition Pittsburgh, PA 15213 USA has been replicated with a variety of stimuli, e.g., upright vs. rotated numbers and familiar upright “live” vs. upside-down “dead” elephants (Wolfe, 2001). While the character И is unfamiliar to English-speakers, for someone familiar with the Cyrillic alphabet, И is a fa- miliar letter. One may therefore predict that familiarity with the Cyrillic alphabet would lead to efficient search for a N among И’s. This is indeed the case (Malinowski & Hubner, 2001). But notice the confound. For English-speakers, N is not just a familiar percept. Rather, it has meaning as the letter “N. ” The symbol И is not only unfamiliar perceptu- ally, it is also meaningless. Among the bilinguals tested by Malinowki & Hubner, both N and И were familiar, and both were meaningful as letters with sounds /n/ and /i:/ respec- tively. If the difficulty English-speakers have searching through И’s arises from a lack of experience, then perform- ance can improve with additional exposure (in effect mak- ing the stimuli familiar). If, on the other hand, the difference is due to categorical status (a difference in meaningfulness), then simply getting participants to treat the unfamiliar sym- bols as members of a category, can lead to more efficient search. The first aim of the present work is tease apart these alternatives by using a classic perceptual task (visual search) and manipulating category membership while controlling for perceptual novelty. Abstract Familiar objects are more easily processed than unfamiliar ob- jects. Familiar objects are also generally meaningful, and comprise members of named categories. Previous work exam- ining familiarity effects in visual processing has confounded perceptual experience with meaningfulness and with name- ability. The present experiments use the visual search para- digm to (1) manipulate category membership while control- ling for novelty and perceptual similarity, and (2) investigate the role of on-line linguistic labels on visual perception. Search performance is dramatically improved when partici- pants are simply told to think of novel stimuli as members of a familiar category. Search performance is further improved when targets or distractors are named compared to trials on which target and distractor identity is known, but the stimuli are not verbally labeled. Keywords: categorization; visual perception; visual search; language; labeling Introduction Familiar stimuli are not simply perceived, but are quickly categorized as members of meaningful categories (e.g., Grill-Spector & Kanwisher, 2005). It might therefore seem surprising that theories of visual perception have for a long time ignored the possible contributions of conceptual cate- gories to visual perception (Wolfe & Horowitz, 2004 for discussion). One reason for this seeming oversight is that familiarity and category membership are correlated. Stimuli that are conceived as being members of a category are gen- erally also ones that participants have experienced before. Conversely, unfamiliar stimuli are not only perceptually unfamiliar, but also meaningless. Finding that participants are poorer at processing unfamiliar stimuli may be merely the function of their novelty. Alternatively, poor perform- ance on unfamiliar stimuli may be due to a failure to repre- sent them as meaningful category members. Discriminating between these alternatives can help us understand the nature of bottom-up and top-down processes in perception. An example helps to clarify this distinction. Frith (1974) found that searching for the unfamiliar target И among N’s is very efficient, while searching for the familiar N among unfamiliar И’s is quite difficult (see also Wang, Cavanagh, & Green, 1994). If the distractors are unfamiliar (И), search is hard. If they are familiar (N), search is easy. 1 This result Additional work has shown that the major determinant of search efficiency in tasks like these is familiarity of the distractors, with the status of the target having minimal effect (Rauschenberger & Yantis, 2006). The most obvious reason why distractor identity is Categories and Perception The impact of categorization on perception has been ex- plored most thoroughly in the aptly named field of categori- cal perception. The most common finding is that practice discriminating between stimuli by placing them into sepa- rate categories increases between-category perceptual dif- ferences, and sometimes decreases within-category differ- ences (Goldstone, 1994; 1998). While this work has shown how perceptual representations can be shaped by experi- ence, less effort has been made to understand the contribu- tion of conceptual categories to perception, controlling for perceptual familiarity. The question whether category membership affects per- formance in visual search, the paradigm used here, has gen- erally taken the form of manipulating the categorical rela- tionship between targets and distractors. Most famously, Jonides and Gleitman (1972) demonstrated that “O” labeled as an “oh” is easier to find among numbers than letters, while the reverse is true for a “O” labeled as a “zero. ” This finding, however, has failed multiple attempts at replication (Duncan, 1983; cf. Taylor & Hamm, 1997). More generally, more important than target identity is that there is at most one tar- get, but numerous distractors.