Accommodating variation: dialects, idiolects, and speech processing

Listeners are faced with enormous variation in pronunciation, yet they rarely have difficulty understanding speech. Although much research has been devoted to figuring out how listeners deal with variability, virtually none (outside of sociolinguistics) has focused on the source of the variation itself. The current experiments explore whether different kinds of variation lead to different cognitive and behavioral adjustments. Specifically, we compare adjustments to the same acoustic consequence when it is due to context-independent variation (resulting from articulatory properties unique to a speaker) versus context-conditioned variation (resulting from common articulatory properties of speakers who share a dialect). The contrasting results for these two cases show that the source of a particular acoustic-phonetic variation affects how that variation is handled by the perceptual system. We also show that changes in perceptual representations do not necessarily lead to changes in production.     

A rose in any other font would not smell as sweet: effects of perceptual fluency on categorization

Fluency--the ease with which people process information--is a central piece of information we take into account when we make judgments about the world. Prior research has shown that fluency affects judgments in a wide variety of domains, including frequency, familiarity, and confidence. In this paper, we present evidence that fluency also plays a role in categorization judgments. In Experiment 1, participants judged a variety of different exemplars to be worse category members if they were less fluent (because they were presented in a smaller typeface). In Experiment 2, we found that fluency also affected judgments of feature typicality. In Experiment 3, we demonstrated that the effects of fluency can be reversed when a salient attribution for reduced fluency is available (i.e., the stimuli are hard to read because they were printed by a printer with low toner). In Experiment 4 we replicated these effects using a within-subject design, which ruled out the possibility that the effects were a statistical artifact caused by aggregation of data. We propose a possible mechanism for these effects: if an exemplar and its category are closely related, activation of one will cause priming of the other, leading to increased fluency. Over time, feelings of fluency come to be used as a valid cue that can become confused with more traditional sources of information about category membership.     

Graspability and object processing in infants

This review pursues the idea that a dual visual system approach is fruitful for interpreting work on infant cognition. We provide examples from the visual perception and cognition literature demonstrating that the potential graspability of stimuli typically used in infant studies influence how these stimuli are processed by the infant brain. Specifically, we argue that small, local, familiar and moving stimuli are more likely to be processed by the dorsal (how or action) stream of visual processing. In contrast, larger, stationary objects are likely to be processed by the ventral (what or perception) stream. This analysis clarifies apparently conflicting results in the literature.     

A new definition of well-behaved discrimination functions

A discrimination function shows the probability or degree with which stimuli are discriminated from each other when presented in pairs. In a previous publication [Kujala, J.V., & Dzhafarov, E.N. (2008). On minima of discrimination functions. Journal of Mathematical Psychology, 52, 116–127] we introduced a condition under which the conformity of a discrimination function with the law of Regular Minimality (which says, essentially, that “being least discriminable from” is a symmetric relation) implies the constancy of the function’s minima (i.e., the same level of discriminability of every stimulus from the stimulus least discriminable from it). This condition, referred to as “well-behavedness,” turns out to be unnecessarily restrictive. In this note we give a significantly more general definition of well-behavedness, applicable to all Hausdorff arc-connected stimulus spaces. The definition employs the notion of the smallest transitively and topologically closed extension of a relation. We provide a transfinite-recursive construction for this notion and illustrate it by examples.     

Regular Minimality and Thurstonian-type modeling

A Thurstonian-type model for pairwise comparisons is any model in which the response (e.g., “they are the same” or “they are different”) to two stimuli being compared depends, deterministically or probabilistically, on the realizations of two randomly varying representations (perceptual images) of these stimuli. The two perceptual images in such a model may be stochastically interdependent but each has to be selectively dependent on its stimulus. It has been previously shown that all possible discrimination probability functions for same–different comparisons can be generated by Thurstonian-type models of the simplest variety, with independent percepts and deterministic decision rules. It has also been shown, however, that a broad class of Thurstonian-type models, called “well-behaved” (and including, e.g., models with multivariate normal perceptual representations whose parameters are smooth functions of stimuli) cannot simultaneously account for two empirically plausible properties of same–different comparisons, Regular Minimality (which essentially says that “being least discriminable from” is a symmetric relation) and nonconstancy of the minima of discrimination probabilities (the fact that different pairs of least discriminable stimuli are discriminated with different probabilities). These results have been obtained for stimulus spaces represented by regions of Euclidean spaces. In this paper, the impossibility for well-behaved Thurstonian-type models to simultaneously account for Regular Minimality and nonconstancy of minima is established for a much broader notion of well-behavedness applied to a much broader class of stimulus spaces (any Hausdorff arc-connected ones). The universality of Thurstonian-type models with independent perceptual images and deterministic decision rules is shown (by a simpler proof than before) to hold for arbitrary stimulus spaces.     

Facilitation of learning of a simultaneous discrimination between rotated patterns by bumblebees

The failure to discriminate between a pattern consisting of four orthogonal bars and the same pattern rotated by 45° has been interpreted in the literature as evidence against pictorial representations in honeybees. This study determines whether prior training can facilitate the discrimination. In Experiment 1, one group of bumblebees was trained with a rewarding spiral pattern (S+) vs. its unrewarding 45° rotation (S−). A second group was trained with two different patterns, the spiral (S+) and the chevron (S−). Both groups were then tested with the spiral and its rotation, both of which were unrewarding. The first group failed in the discrimination while the second succeeded. The same was true when the training period was defined by choice frequency instead of time (Experiment 2). The facilitation due to prior experience was pattern specific (Experiments 3 and 4). These results show perceptual learning in bumblebees and weaken the case against pictorial representations.     

Inter-species variation in colour perception

Inter-species variation in colour perception poses a serious problem for the view that colours are mind-independent properties. Given that colour perception varies so drastically across species, which species perceives colours as they really are? In this paper, I argue that all do. Specifically, I argue that members of different species perceive properties that are determinates of different, mutually compatible, determinables. This is an instance of a general selectionist strategy for dealing with cases of perceptual variation. According to selectionist views, objects simultaneously instantiate a plurality of colours, all of them genuinely mind-independent, and subjects select from amongst this plurality which colours they perceive. I contrast selectionist views with relationalist views that deny the mind-independence of colour, and consider some general objections to this strategy.     

Perceptual Learning

The extent of adult improvement in not only complex but also simple perceptual tasks is remarkable. Although this phenomenon has been noted and studied since the middle of the 19th century, recent advances in the study of brain physiology and anatomy afford new insights. Improvement specificity suggests that changes involve early sensory cortical areas, previously thought to lose their plasticity following the first years. The critical role of selective attention, even in learning the simplest tasks, as well as the precedence of learning easy cases, suggests the involvement of high-level cortical areas. Learning easy cases is more general than learning difficult cases. This pattern suggests the involvement of both high- and low-level areas in an orderly manner, with easy learning beginning at high-level areas and harder cases being resolved by access to low-level areas. The mapping of behavioral findings to underlying brain sites provides a unified framework for this interdisciplinary field.     

Superior discrimination between similar stimuli after simultaneous exposure

Human participants received unsupervised exposure to difficult-to-discriminate chequerboard stimuli (e.g., AX and BX), before learning a discrimination between them. Experiment 1 demonstrated that prior exposure enhanced later discrimination and that intermixed exposure (AX, BX, AX, BX …) resulted in better subsequent discrimination than did blocked exposure (CY, CY … DY, DY …). Experiment 2 showed that simultaneous exposure to two similar stimuli (AX–BX, BX–AX …) facilitated the later acquisition of a successive discrimination, more than successive exposure (AX–AX, BX–BX …). These results parallel those observed by Mundy, Honey, and Dwyer (2007) who used pictures of human faces as stimuli and establish the generality of the fact that simultaneous exposure produces a particularly marked perceptual learning effect.     

Development of parafoveal processing within and across words in reading: Evidence from the boundary paradigm

In this study we used the boundary paradigm to examine whether readers extract more parafoveal information within than across words. More specifically, we examined whether readers extract more parafoveal information from a compound word's second constituent than from the same word when it is the noun in an adjective–noun phrase (kummitustarina “ghost story” vs. lennokas tarina “vivid story”). We also examined whether the processing of compound word constituents is serial or parallel and how parafoveal word processing develops over the elementary school years. Participants were Finnish adults and 8-year-old second-, 10-year-old fourth-, and 12-year-old sixth-graders. The results showed that for all age groups more parafoveal information is extracted from the second constituent within compounds than from the noun in adjective–noun phrases. Moreover, for all age groups we found evidence for parallel processing of constituents within compounds, but only when the compounds were of high frequency. In sum, the present study shows that attentional allocation extends further to the right and is more simultaneous when words are linguistically and spatially unified, providing evidence that attention in text processing is flexible in nature.