What information is necessary for speech categorization? Harnessing variability in the speech signal by integrating cues computed relative to expectations

Most theories of categorization emphasize how continuous perceptual information is mapped to categories. However, equally important are the informational assumptions of a model, the type of information subserving this mapping. This is crucial in speech perception where the signal is variable and context dependent. This study assessed the informational assumptions of several models of speech categorization, in particular, the number of cues that are the basis of categorization and whether these cues represent the input veridically or have undergone compensation. We collected a corpus of 2,880 fricative productions (Jongman, Wayland, & Wong, 2000) spanning many talker and vowel contexts and measured 24 cues for each. A subset was also presented to listeners in an 8AFC phoneme categorization task. We then trained a common classification model based on logistic regression to categorize the fricative from the cue values and manipulated the information in the training set to contrast (a) models based on a small number of invariant cues, (b) models using all cues without compensation, and (c) models in which cues underwent compensation for contextual factors. Compensation was modeled by computing cues relative to expectations (C-CuRE), a new approach to compensation that preserves fine-grained detail in the signal. Only the compensation model achieved a similar accuracy to listeners and showed the same effects of context. Thus, even simple categorization metrics can overcome the variability in speech when sufficient information is available and compensation schemes like C-CuRE are employed.     

Revisiting the agentic shift: Weakening personal control increases susceptibility to social influence

What happens when people experience a reduced sense of personal control? Among the various strategies to defend against a perception of randomness, people may show an increased acceptance of external sources of control. Indeed, in one of the most classic studies in social psychology, Stanley Milgram referred to an “agentic shift”—the tendency to relinquish personal control to an external agent—to explain his dramatic obedience effects. We propose that his account is a specific manifestation of a more general phenomenon: the tendency for increased susceptibility to various forms of external social influence when perceived personal control is reduced. In a series of (lab and field) studies using a variety of perceived control manipulations, we demonstrate that a reduction in the sense of personal control increases people's vulnerability to the bystander effect, promotes obedience to authority and fosters compliance with behavioral requests. Copyright © 2012 John Wiley & Sons, Ltd.     

Inhibitory control gains from higher-order cognitive strategy training

The present study examined the transfer of higher-order cognitive strategy training to inhibitory control. Middle school students enrolled in a comprehension- and reasoning-focused cognitive strategy training program and passive controls participated. The training program taught students a set of steps for inferring essential gist or themes from materials. Both before and after training or a comparable duration in the case of the passive controls, participants completed a semantically cued Go/No-Go task that was designed to assess the effects of depth of semantic processing on response inhibition and components of event-related potentials (ERP) related to response inhibition. Depth of semantic processing was manipulated by varying the level of semantic categorization required for response selection and inhibition. The SMART-trained group showed inhibitory control gains and changes in fronto-central P3 ERP amplitudes on inhibition trials; whereas, the control group did not. The results provide evidence of the transfer of higher-order cognitive strategy training to inhibitory control and modulation of ERPs associated with semantically cued inhibitory control. The findings are discussed in terms of implications for cognitive strategy training, models of cognitive abilities, and education.     

Identifying the ‘if’ for ‘if-then’ plans: Combining implementation intentions with cue-monitoring targeting unhealthy snacking behaviour

Implementation intentions aimed at changing unwanted habits require the identification of personally relevant cues triggering the habitual response in order to be effective. To facilitate successful implementation intention formation, in the present study, planning was combined with cue-monitoring, a novel way to gain insight into triggers for unhealthy snacking. It was tested whether keeping a cue-monitoring diary and tailoring implementation intentions accordingly improves plan effectiveness. A 2 Monitoring (cue-monitoring, control)?×?2 Planning (implementation intention, goal intention) between subjects design was adopted. Participants (N = 161) monitored their unhealthy snacking behaviour for a week using either a cue-monitoring or a control diary. Participants then formulated a goal intention or an implementation intention tailored to their personal cue. Snacking frequency and caloric intake from unhealthy snacks were examined using a seven-day snack diary. The results did not indicate an interaction but yielded a main effect of Monitoring. Cue-monitoring either or not combined with implementation intentions reduced unhealthy snacking behaviour compared with control. Findings emphasise the effectiveness of cue-monitoring, suggesting that on the short term, cue-monitoring suffices to decrease unhealthy snacking, without additional benefit from planning. Future research should examine whether supplementing cue-monitoring with implementation intentions is required to establish long-term behaviour change maintenance.     

When similarity and causality compete in category-based property generalization

Five experiments were performed to investigate the category-based generalization of nonblank properties, properties that were novel but that were attributed to existing category features with causal explanations. Experiments 1-3 tested how such explanations interact with the well-known effects of similarity on such generalizations. The results showed that when the causal explanations were used, standard effects of typicality (Experiment 1), diversity (Experiment 2), or similarity itself (Experiment 3) were almost completely eliminated. Experiments 4 and 5 demonstrated that category-based generalizations exhibit some of the standard properties of causal reasoning; for example, an effect (i.e., a novel category property) is judged to be more prevalent when its cause (i.e., an existing category feature) is also prevalent. These findings suggest that category-based property generalization is often an instance of causal inference.     

Gradient effects of within-category phonetic variation on lexical access

In order to determine whether small within-category differences in voice onset time (VOT) affect lexical access, eye movements were monitored as participants indicated which of four pictures was named by spoken stimuli that varied along a 0-40 ms VOT continuum. Within-category differences in VOT resulted in gradient increases in fixations to cross-boundary lexical competitors as VOT approached the category boundary. Thus, fine-grained acoustic/phonetic differences are preserved in patterns of lexical activation for competing lexical candidates and could be used to maximize the efficiency of on-line word recognition.     

Eyetracking and selective attention in category learning

An eyetracking version of the classic Shepard, Hovland, and Jenkins (1961) experiment was conducted. Forty years of research has assumed that category learning often involves learning to selectively attend to only those stimulus dimensions useful for classification. We confirmed that participants learned to allocate their attention optimally. We also found that learners tend to fixate all stimulus dimensions early in learning. This result obtained despite evidence that participants were also testing one-dimensional rules during this period. Finally, the restriction of eye movements to only relevant dimensions tended to occur only after errors were largely (or completely) eliminated. We interpret these findings as consistent with multiple-systems theories of learning which maximize information input in order to maximize the number of learning modules involved, and which focus solely on relevant information only after one module has solved the learning problem.     

Infants are sensitive to within-category variation in speech perception

Previous research on speech perception in both adults and infants has supported the view that consonants are perceived categorically; that is, listeners are relatively insensitive to variation below the level of the phoneme. More recent work, on the other hand, has shown adults to be systematically sensitive to within category variation [McMurray, B., Tanenhaus, M., & Aslin, R. (2002). Gradient effects of within-category phonetic variation on lexical access, Cognition, 86 (2), B33-B42.]. Additionally, recent evidence suggests that infants are capable of using within-category variation to segment speech and to learn phonetic categories. Here we report two studies of 8-month-old infants, using the head-turn preference procedure, that examine more directly infants' sensitivity to within-category variation. Infants were exposed to 80 repetitions of words beginning with either /b/ or /p/. After exposure, listening times to tokens of the same category with small variations in VOT were significantly different than to both the originally exposed tokens and to the cross-category-boundary competitors. Thus infants, like adults, show systematic sensitivity to fine-grained, within-category detail in speech perception.     

Instructions for Authors

Instructions for Authors

Instructions for Authors