Donald G. Jamieson

Training non-native speech contrasts in adults: Acquisition of the English /ð/-/θ/ contrast by francophones

Speech perception abilities are modified by linguistic experience to maximize sensitivity to acoustic contrasts that are important for one’s linguistic community, while reducing sensitivity to other acoustic cues. Although some of these changes may be irreversible, in other cases adults may learn to perceive non-native speech sounds in a linguistically meaningful manner with limited perceptual training. The present study investigates the possibility of using a technique based on perceptual fading to train Canadian francophone adults to distinguish the voiced and voiceless “th” sounds of English: Ið/, as in “the,” versus Iθ/, as in “theta.” Following a pretest to measure identification and discrimination performance with both natural and synthetic speech tokens, 10 subjects were trained using synthetic stimuli. Approximately 90 min of this training improved performance with both natural and synthetic tokens relative to that of untrained control subjects. The results suggest that there is a much higher degree of plasticity in these acoustic/linguistic categories than would be inferred from the normal performance of Canadian francophones who learn English as adults. The nature of the training technique is discussed in relation to other training paradigms.

Resolution time and the coding of arithmetic relations on supraliminally different visual extents

Abstract Comparison time for pairs of vertical-line stimuli, sufficiently different that they can be errorlessly discriminated with respect to visual extent, was examined as a function of arithmetic relations (physical ratio and difference) on members of the pair. Arithmetic relations are coded very precisely by judgment time: Responses slow as stimulus ratios approach one with difference fixed, and as stimulus differences approach zero with ratio fixed. Most models which assume a simple (Difference or Ratio) resolution rule operating on independent sensations require judgment time to depend on either ratios or on differences but not on both. Further tests showed both an index based on median judgment times and a confusion index based on pairs of observed judgment times, satisfied the requirements for a Positive Difference Structure. One representation of these data, which remains acceptable through all analyses, is a Difference resolution rule operating on sensations determined by a power psychophysical function with β L ( x , y ) = F { ψ ( x ) − ψ ( y )} + R , where L ( x , y ) is the judgment time with the stimulus pair x and y , ψ ( x ) = Ax β + C , R is a positive constant, and F is a continuous monotone decreasing function.

Feedback versus an Illusion in Time

The accuracy of many perceptual comparisons depends greatly on the order in which the to-be-compared stimuli are presented. With comparisons of durations around 300 ms, these presentation-order effects do not diminish, even with extended practice, when feedback about response accuracy is withheld. Providing such feedback greatly diminishes presentation-order effects and coincidentally produces substantial increases in response accuracy. The feedback acts in part through inducing response biases and in part through changes in sensitivity. The contradiction between studies which report time-order errors in duration comparison and those which do not is attributable to differences in the use of information feedback.

Evaluating pictographs using semantic differential and classification techniques

Three experiments confirm the appropriateness of the semantic differential technique as a method for measuring the extent to which various public information pictographic signs convey their intended meaning. A general classification technique, which minimizes preliminary testing, was shown to be an efficient method for measuring the similarity of meaning of pictographs to their intended lettered translation. Application of this classification technique was illustrated by examining the contribution of components of the pictographic signs to the conveyed meaning.

Preference and the time to choose

Abstract Monotone relations between two measures of choice behavior, response probability and response latency, were found in four preferential choice situations: Response time decreased monotonically as response probability increased. These data suggest that choice time may be quite generally substitutable for choice probability, substantially reducing the expense of time and effort required to study preferential choice behavior and to test probabilistic theories of preferential choice. The result that the relation between the time to choose on the initial choice instance (first replication) and the subsequent frequency of choice was also monotone decreasing indicates that consideration of the time to choose, in addition to which choice is made, can improve the precision with which preferences are identified (for example, in an opinion poll). The importance of choice time to the prediction of future choice behavior was demonstrated in a further analysis which showed that initial choices occurring with response times falling in the fastest quartile of the choice time distribution were repeated on almost every subsequent choice opportunity, while choices occurring with latencies falling in the slowest quartile were equally likely to occur only rarely as consistently on subsequent opportunities.

Locus of selective adaptation in speech perception.

Voiced (/ba/ or /da/) and voiceless (/pa/ or /ta/) consonants seem to affect different auditory system loci. On a voice-onset-time continuum (/ba/ to /pa/ or /da/ to /ta/) the selective adaptation effects produced by voiceless consonants are largely ear-independent and endure over delays of at least 1 min. However, voiced adapters produce selective adaptation effects that are highly ear-specific and relatively short-lived (less than 15 s). These differences suggest that specific cues to voiced and voiceless consonant sounds are processed by distinct auditory mechanisms and that these processes occur at different levels of the auditory system. One mechanism, which processes cues to voiced consonants, is peripheral and ear-specific. The second mechanism, which processes cues to voiceless consonants, is central and ear-independent.

Studying preferential choice without stable probability estimates: temporal transitivity analyses

Abstract The possibility of using choice-response times to study unidimensional preferential choice was investigated. Analyses of temporal transitivity relations among stochastically dominant responses confirmed that, in the absence of sufficient replications for the reliable estimation of choice probabilities, choice time does provide a valuable method for evaluating preferential choice theories. Laterality effects in these transitivity analyses provided strong support for the probabilistic stimulus structure of Coombs unfolding theory of preferential choice, and disconfirmed Bechtels version of unfolding theory. These laterality effects were diminished by increasing psychological distance, as predicted by Coombs formulation.

Studies of Possible Psychoacoustic Factors Underlying Speech Perception

As with all sounds which are presented to the ear, speech sounds are subject to processing by the auditory system. Thus, whatever their importance for the listener, whatever the message conveyed, and however the listener may use linguistic knowledge, context, or other non-acoustic cues to assist in decoding the message from a speaker, the speech sounds which are presented to the listener’s ear are subject to the same “obligatory processing” as are nonspeech sounds. In some situations, we might expect that such obligatory processing would result in the diminution of the perceptual salience of an acoustic cue—for example, as a consequence of masking between two portions of a signal. In other circumstances, we might expect that the auditory system would enhance the perceptual salience of an acoustic cue—for example, as a consequence of spectral-temporal integration. Of course the extent to which both perceptual factors and higher-order variables influence the responses which are actually observed in an experiment will reflect the demands of the particular task which is set for the listener (cf., the paper by MacMillan, Braida, Goldberg, and Khazatsky, in this volume, for further discussion of this point).

A digital sound editor.

A series of digital computer programs which facilitate the production and control of acoustic stimuli for hearing assessment and research are described. The package, which is available for PDP 11 computers under RT-11, allows sounds to be digitized, adjusted for amplitude and/or dc offset, edited while in digital form, and output to file or tape. The waveform editor package includes facilities to edit sounds in time--with some sections removed or added with temporal precision of 0.1 msec or better. Two or more sounds may also be combined for stereo or monaural (sound-on-sound) output, or two may be concatenated. Together, the programs permit a wide range of manipulations useful in preparing sound stimuli for use in hearing experiments or in clinical audiometry.

Visual influence on taste sensitivity

A claimed dependence of taste sensitivity on body state, accepted for 40 years, is investigated in two experiments. Neither the growth of sensation above threshold, as measured in a magnitude estimation experiment, nor taste sensitivity near threshold, as measured by a signal detection analysis, show the claimed increment when individuals are dark-adapted. On the contrary, in both cases, performance is superior in the light, when subjects taste with their eyes open, possibly due to an arousing effect of concurrent visual stimulation.