Grounding Natural Language Quantifiers in Visual Attention

Grounding Natural Language Quantifiers in Visual Attention. Kenny R. Coventry 1 (kcoventry@plymouth.ac.uk), Angelo Cangelosi 2 (acangelosi@plymouth.ac.uk), Stephen Newstead 1 (snewstead@plymouth.ac.uk), Alison Bacon 1 (ambacon@plymouth.ac.uk), and Rohanna Rajapakse 2 (rrajapakse@plymouth.ac.uk). Centre for Thinking and Language, School of Psychology, & 2 Adaptive Behaviour and Cognitive Group, School of Computing, Communications and Electronics, University of Plymouth Devon, PL4 8AA England (UK) The Origins of Context Effects Given these myriad context effects, while some have argued that number is critical for quantifier comprehension, others have proposed that quantifiers are not about number at all (Moxey & Sanford, 1993). Yet, clearly as the number of objects increases, the appropriateness of high magnitude quantifiers increases. There are two key issues emerging from this debate. First, the existence of context effects is important in its own right, but discussion of the issue of where such effects come from is noticeably absent from this literature. Why is it that set size, expected frequency, relative size etc. matter? The second issue is intricately bound up with the answer to this question. It has been assumed in the quantifier literature that the actual number of objects in a scene being described is the number used to map onto comprehension of vague quantifiers. Yet there is much evidence that, under time pressure conditions, people do not give very accurate judgments about the number of objects there are in a scene. When a small number of objects is presented in a visual scene, we are able to know the number of objects present almost instantly (an effect called subitizing in the number literature). However, when the number of objects increases, we are much less accurate in our judgments of how many objects there are in a visual scene. Hence, we will argue that in the quantifier literature the lack of success of scalar approaches to quantifiers, and the corresponding abandonment of this approach, has been a result of a conflation of number with the actual number of objects being referred to. We will show that the “psychological” numbers returned from visual attentional constraints under time pressure allow number to predict the appropriateness of natural language quantifiers much more successfully. Specifically, in three experiments we uncover several new context effects for vague quantifiers and show that the same effects also occur for number judgments. However, we first briefly overview the literature on object enumeration with a view to predicting these new context effects. Abstract The literature on vague quantifiers in English (words like “some”, “many”, etc.) is replete with demonstrations of context effects. Yet little attention has been paid to the issue of where such effects come from. We explore the possibility that they emanate from a visual attentional bottleneck which limits the accuracy of judgments of number in visual scenes under conditions of time pressure. We present the results of 3 experiments which reveal a range of new context effects on the acceptability of vague quantifiers to describe a number of objects in a visual scene, and show corresponding effects on judgments of number using the same visual scenes under speeded conditions. Introduction Talking about numbers of objects in a visual scene often involves the use of descriptions of quantity which are vague. Furthermore, quantifiers, whether they be of number (e.g., many), amount (e.g., much), or time/frequency (e.g., often) pervade natural language, and therefore constitute an essential part of the lexicon for the child to acquire, and consequently for integration into NL systems. An understanding of quantifiers is often largely couched in terms of the notion that quantifiers refer to points on a scale. In its most extreme form, the temptation is to treat quantifiers in terms of a quantifier-to-number mapping (e.g., Bass, Cascio & O’Connor, 1984; Reyna, 1981). In computational terms, a scene can be parsed for the number of entities present, and the mapping between the number and the quantifier associated with the appropriate point on the scale can be easily achieved. However, there is compelling evidence that the comprehension and production of quantifiers is affected by a range of factors which go beyond the number of objects present, including the relative size of the objects involved in the scene (e.g., Hormann, 1983, Newstead & Coventry, 2000), the expected frequency of those objects based on prior experience (e.g., Moxey & Sanford, 1993), the functionality present in the scene (Newstead & Coventry, 2000), and the need to control the pattern of inference of those involved in the communication (e.g., Moxey, Sanford & Dawydiak, 2001). To give an example of one of these context effects (expected frequency in this case), a few people outside a cinema is associated with more people than a few people outside a fire station (Moxey & Sanford, 1993). Visual Object Enumeration There is much evidence that participants do not give very accurate numerosity judgements under time pressure. These studies have revealed at least three strategies used by the brain: a fast and accurate processing of small groups of four or fewer items in almost constant response time (subitizing),