Distinctive feature control of decision time: Same-different judgments of simultaneously heard phonemes

Ss decided whether dichotically presented consonant or vowel phonemes were “same” or “different” in a reaction time (RT) task. Results indicated that “different” responses were made on the basis of a serial, self-terminating scan of distinctive feature differences between phonemes. “Same” responses were considered too fast to be accounted for by this process and were discussed as a separate parallel process. Recognition of dichotically presented syllables appears to involve a third process in which phonemes are also identified in terms of their distinctive features.     

The logic of misperceived distance (or location) theories of the Poggendorff illusion

For the Poggendorff display (transversal interrupted by parallel lines), the typical distance-misperception theory postulates that a particular linear distance extending across the empty space between parallels is underestimated; examples are the intertransversal slant distance defined by the closest ends of the transversal segments (a “wings-in Müller-Lyer like” underestimation) or the perpendicular distance between parallels (parallels “attract”). Distance misperception by itself, however, can neither establish that perceived transversal misalignment exists for a Poggendorff display nor specify the perceivedlocation conditions) that will produce perceptual collinearity. The perceptual displacement vector is introduced as a means of specifying fully the perceptual mislocation (displacement) of one transversal segment with respect to the other. Given this vector information (direction as well as distance), the logical soundness of theories postulating distance or location misperception were evaluated, and they were compared on the basis of extant data. Such vector information can be used to evaluate other classes of theories as well.     

The “lag effect” in dichoptic viewing

Ten subjects were asked to report both of two different consonant-vowels (CVs) presented to the same foveal area, but in different eyes (“dichoptically”). Stimuli were presented at stimulus-onset asynchronies (SOAs) ranging from 0 to 150 msec in 25-msec steps. Correct identifications were significantly depressed for the eye receiving the leading stimulus at SOAs of 25 to 75 msec. Monoptic data from three subjects indicated no significant reductions in correct identification as a function of SOA. The dichoptic results can be understood in terms of current theories of visual backward masking and are similar to the “lag effect” observed with dichotic listening to speech stimuli. Similarity of results for the two modalities suggests a similar “two-process” explanation may underlie both phenomena.     

On the perception of symmetrical and repeated patterns

Four experiments investigated rapid perceptual judgments about tachistoscopically presented patterns that were either symmetrical about or repeated across a vertical axis. The same patterns were presented under two different instructional conditions; some Ss were to judge the two halves of each pattern “same” or “mirror,” others were to judge each pattern as a whole “symmetrical” or “asymmetrical.” With dot patterns, RTs were faster for symmetrical than for repeated patterns when the two halves were close together, but not when they were separated, regardless of instructions. With simpler patterns made up of arrowheads and C-shapes, however, “same” RTs were faster than “mirror,” but “asymmetrical” RTs were marginally slower than “symmetrical,” regardless of spatial separation. The advantage of “same” over “mirror” did not seem to be simply a labeling effect. The results suggest that left-right symmetry is perceptually more salient than left-right repetition when the patterns are perceived holistically. By contrast, distinct patterns can be matched more rapidly when they are the same than when they are left-right mirror images.     

“Hearing voices”: Auditory hallucinations as failure of top‐down control of bottom‐up perceptual processes

Auditory hallucination is a key characteristic of schizophrenia that seriously debilitates the patient, with consequences for social engagement with others. Hallucinatory experiences are also observed in healthy individuals in the general population who report “hearing voices” in the absence of an external acoustic input. A view on auditory hallucinations and “hearing voices” is presented that regards such phenomena as perceptual processes, originating from speech perception areas in the left temporal lobe. Healthy individuals “hearing voices” are, however, often aware that the experience comes from inner thought processes, which is not reported by hallucinating patients. A perceptual model can therefore, not alone explain the difference in the phenomenology of how the “voices heard” are attributed to either an inner or outer cause. An expanded model is thus presented which takes into account top‐down cognitive control, localized to prefrontal cortical areas, to inhibit and re‐attribute the perceptual mis‐representations. The expanded model is suggested to be empirically validated using a dichotic listening speech perception paradigm with instructions for top‐down control of attention focus to either the right or left side in auditory space. It is furthermore suggested to use fMRI to validate the temporal and frontal lobe neuronal correlates of the cognitive processes involved in auditory hallucinations.     

Bottom-up effects modulate saccadic latencies in well-known eye movement paradigm

A well-known eye movement paradigm combines saccades (fast eye movements) with a perceptual discrimination task. At a variable time after the onset of a central arrow cue indicating the target direction [the stimulus onset asynchrony (SOA)], discrimination symbols appear briefly at saccade target and non-target locations. A previous study revealed an unexpected effect of SOA on saccadic latencies: latencies were longer in trials with longer SOAs. It was suggested that this effect reflects a top-down process as observers may wait for the discrimination symbol to appear before executing saccades. However, symbol onsets may also modulate saccade latencies from the bottom-up. To clarify the origin of the SOA effect on latencies in this paradigm, we used a simplified version of the original task plus two new symbol onset conditions for comparison. The results indicate that the modulation of saccadic latencies was not due to a top-down strategy, but to a combination of two opposing bottom-up effects: the symbol onsets at the target location shortened saccade latencies, while symbol onsets at non-target locations lengthened saccade latencies.     

Generalization in perceptual learning for speech

Lexical context strongly influences listeners’ identification of ambiguous sounds. For example, a sound midway between /f/ and /s/ is reported as /f/ in “sheri_’” but as /s/ in “Pari_.” Norris, McQueen, and Cutler (2003) have demonstrated that after hearing such lexically determined phonemes, listeners expand their phonemic categories to include more ambiguous tokens than before. We tested whether listeners adjust their phonemic categories for a specific speaker: Do listeners learn a particular speaker’s “accent”? Similarly, we examined whether perceptual learning is specific to the particular ambiguous phonemes that listeners hear, or whether the adjustments generalize to related sounds. Participants heard ambiguous /d/ or /t/ phonemes during a lexical decision task. They then categorized sounds on /d/-/t/ and /b/-/p/ continua, either in the same voice that they had heard for lexical decision, or in a different voice. Perceptual learning generalized across both speaker and test continua: Changes in perceptual representations are robust and broadly tuned.     

Perceptual equivalence of acoustic cues in speech and nonspeech perception

Trading relations show that diverse acoustic consequences of minimal contrasts in speech are equivalent in perception of phonetic categories. This perceptual equivalence received stronger support from a recent finding that discrimination was differentially affected by the phonetic cooperation or conflict between two cues for the /slIt/-/splIt/contrast. Experiment 1 extended the trading relations and perceptual equivalence findings to the /sei/-/stei/contrast. With a more sensitive discrimination test, Experiment 2 found that cue equivalence is a characteristic of perceptual sensitivity to phonetic information. Using “sine-wave analogues” of the /sei/-/stei/stimuli, Experiment 3 showed that perceptual integration of the cues was phonetic, not psychoacoustic, in origin. Only subjects who perceived the sine-wave stimuli as “say” and “stay” showed a trading relation and perceptual equivalence; subjects who perceived them as nonspeech failed to integrate the two dimensions perceptually. Moreover, the pattern of differences between obtained and predicted discrimination was quite similar across the first two experiments and the “say”-“stay” group of Experiment 3, and suggested that phonetic perception was responsible even for better-than-predicted performance by these groups. Trading relations between speech cues, and the perceptual equivalence that underlies them, thus appear to derive specifically from perception of phonetic information.     

The Embodied Subjective Perspective

Perspective is a distinctive feature of external perception. There is a question of how to account for perceptual constancy in spite of changing perspectives. Alva Noe proposes the notion of ＂perspectival property＂ [P-property] and appeals to the perspectival aspect of perceptual content. His proposal conflicts with perceptual experiences and hence incurs many criticisms. Drawing on Husserl＇s phenomenology and Gibsonian psychology, I propose the notion of ＂perspectival awareness＂ [P-awareness]. I will argue that P-awareness is embodied pre-thematic self-awareness instead of the experience of a special kind of objective property. With the notion of P-awareness in mind, I then elaborate on the embodied subjective feature of perspective.     

Listening for mispronunciations: A measure of what we hear during speech

Ss heard a passage from Lewis Carroll’s Through the Looking Glass and were asked to indicate, as quickly as possible, whenever they heard a mispronunciation. Mispronunciations were produced by changing one consonant sound in a three-syllable word by one, two, or four distinctive features (e.g., busily to “pizily,” “visily,” or “sizily”). Mispronunciations involving a single feature change were seldom detected, while two and four feature changes were readily detected. The syllable in which a mispronunciation occurred did not affect the probability of detecting a mispronunciation. However, reaction times to mispronounced words were at least a third of a second slower when they occurred in the-first syllable of the word. The results were taken to support the notion that words are identified by their distinctive features.     

A central-peripheral asymmetry in masked priming

Masked primes presented prior to a target result in behavioral benefits on incompatible trials (in which the prime and the target are mapped onto opposite responses) when they appear at fixation, but in behavioral benefits on compatible trials (in which the prime and the target are mapped onto the same response) when appearing peripherally. In Experiment 1, the time course of this central-peripheral asymmetry (CPA) was investigated. For central primes, compatible-trial benefits at short stimulus onset asynchronies (SOAs) turned into incompatible-trial benefits at longer SOAs. For peripheral primes, compatible-trial benefits at short SOAs increased in size with longer SOAs. Experiment 2 showed that these effects also occur when primes and targets are physically dissimilar, ruling out an interpretation in terms of the perceptual properties of the stimulus material. In Experiments 3 and 4, the question was investigated as to whether the CPA is related to visual-spatial attention and/or retinal eccentricity per se. The results indicate that the CPA is independent of attentional factors but strongly related to the physiological inhomogeneity of the retina. It is argued that central and peripheral primes trigger an initial motor activation, which is inhibited only if primes are presented at retinal locations of sufficiently high perceptual sensitivity. The results are discussed in terms of an activation threshold model.     

Switching attention between the ears to monitor tones Nigel Harvey

Alternating dichotic presentation of tones was compared with monaural presentation in two different perceptual tasks. When Ss were asked to detect higher frequency target tones in fists of six background tones, they missed less than 5%. However, when the presentation was fast (10/sec) and the tones alternated dichotically, Ss reported “hearing” only three or four tones. In two further experiments, Ss were asked to judge the number of tones or to report their spatial and temporal positions; these tasks were much less accurately performed, for the dichotic lists, than the target detection task. The differing effects of switching rate on these tasks are discussed in relation to the types of processing they require.     

Facilitation and inhibition caused by the orienting of attention in propositional reasoning tasks

In an attempt to study the orienting of attention in reasoning, we developed a set of propositional reasoning tasks structurally similar to Posner's (1980) spatial cueing paradigm, widely used to study the orienting of attention in perceptual tasks. We cued the representation in working memory of a reasoning premise, observing whether inferences drawn using that premise or a different, uncued one were facilitated, hindered, or unaffected. The results of Experiments 1a, 1b, 1c, and 1d, using semantically (1a–1c) or statistically (1d) informative cues, showed a robust, long-lasting facilitation for drawing inferences from the cued rule. In Experiment 2, using uninformative cues, inferences from the cued rule were facilitated with a short stimulus onset asynchrony (SOA), whereas they were delayed when the SOA was longer, an effect that is similar to the “inhibition of return” (IOR) in perceptual tasks. Experiment 3 used uninformative cues, three different SOAs, and inferential rules with disjunctive antecedents, replicating the IOR-like effect with the long SOAs and, at the short SOA, finding evidence of a gradient-like behaviour of the facilitation effect. Our findings show qualitative similarities to some effects typically observed in the orienting of visual attention, although the tasks did not involve spatial orienting.     

Relation of the verbal transformation and the phonemic restoration effects

This study examined the relationship between illusory changes of repeated words (“verbal transformations” or VTs) and illusory presence of phonemes replaced by noise (“phonemic restorations” or PhRs). Separate groups of 20 subjects were each presented with one of four taped variations of the repeated stimulus word “magistrate”: stimulus intact (MAGISTRATE); speech sound “s” removed and replaced with a silent gap (MAGI TRATE); speech sound “s” removed and replaced with a louder extraneous sound (MAGI¹TRATE); syllable “gis” removed and replaced with a louder extraneous sound (MA⁷¹TRATE). The stimuli MAGI¹TRATE and MA⁷¹TRATE evoked PhRs, and with these stimuli, the phonetic changes corresponding to VTs were concentrated at the perceptually restored portions of the word. It is suggested that both PhRs and VTs are related directly to perceptual processes employed normally for the correction of errors and resolution of ambiguities in speech. Other effects of PhRs upon VTs are described and implications of these findings for mechanisms underlying speech perception are discussed.     

Two left-hemisphere mechanisms in speech perception

Right-ear advantages of different magnitudes occur systematically in dichotic listening for different phoneme classes and for certain phonemes according to their syllabic position. Such differences cannot be accounted for in terms of a single mechanism unique to the left hemisphere. Instead, at least two mechanisms are needed. One such device appears to be involved in the auditory analysis of transitions and other aspects of the speech signal. This device appears to be engaged for speech and nonspeech sounds alike. The other mechanism, the more accustomed “speech processor”, appears to make all phonetic decisions in identifying the stimulus.     

Effects of phonological similarity on priming in auditory lexical decision

Two auditory lexical decision experiments were conducted to determine whether facilitation can be obtained when a prime and a target share word-initial phonological information. Subjects responded “word” or “nonword” to monosyllabic words and nonwords controlled for frequency. Each target was preceded by the presentation of either a word or nonword prime that was identical to the target or shared three, two, or one phonemes from the beginning. The results showed that lexical decision times decreased when the prime and target were identical for both word and nonword targets. However, no facilitation was observed when the prime and target shared three, two, or one initial phonemes, These results were found when the interstimulus interval between the prime and target was 500 msec or 50 msec. In a second experiment, no differences were found between primes and targets that shared three, one, or zero phonemes, although facilitation was observed for identical prime-target pairs. The results are compared to recent findings obtained using a perceptual identification paradigm. Taken together, the findings suggest several important differences in the way lexical decision and perceptual identification tasks tap into the information-processing system during auditory word recognition.     

Sentence perception units and levels of syntactic structure

Subjects listened to recorded sentences which were followed by probe words. They performed a next-word naming task—uttering the word that followed the probe word in the original sentence as quickly as possible. Other things being equal, naming latencies are longer when the juncture between the probe word and the response word in the original sentence sequence terminates a “functionally complete” unit than when this position corresponds to the boundary of a “functionally incomplete” unit. These results are not predicted by existent “syntactic” theories of sentence perception units, and these theories are to that extent shown to be inadequate. A “functional” program for the study of sentence perception is suggested.     

Size scaling in two-dimensional pictorial arrays

The study examined effects of instructional sets (objective, phenomenal, projective, and retinal) on the judged sizes of blocks placed at various “distances” in a pictorial array. Magnitude estimations of size were consistent with previous studies of size constancy in three-dimensional arrays. Chronometric analyses indicated that reaction time increased with distal size, but was not affected by perceived distance. The results suggested that size was scaled relative to a perceptual unit. Instructions affected the nature of the scale unit (proximal vs. distal), but not the scaling process itself.