Digit Triplet Research Articles

Development and validation of an automatic speech-in-noise screening test by telephone

To meet the need for an objective self-test for hearing screening, a new Dutch speech-in-noise test was developed. Digit triplets were used as speech material. The test was made fully automatic, was controlled by a computer, and can be done by telephone. It measures the speech reception threshold (triplet SRTn) using an adaptive procedure, in about 3 min. Our experiments showed no significant influence of telephone type or listening environment. Measurement errors were within 1 dB, which makes the test accurate. In additional experiments with hearing-impaired subjects (76 ears of 38 listeners), the new test was compared to the existing sentence SRTn test of Plomp and Mimpen, which is considered to be the standard. The correlation between both SRTns was 0.866. As expected, correlations between the triplet SRTn test by telephone and average pure-tone thresholds are somewhat lower: 0.732 for PTA0.5, 1, 2, and 0.770 for PTA0.5, 1, 2,4. When proper SRTn values were chosen for distinguishing between normal-hearing and hearingimpaired subjects, the triplet SRTn test was found to have a sensitivity of 0.91 and a specificity of 0.93.

Feedback in hypothesis testing: an ERP study.

We used event-related potentials (ERPs) to probe the effects of feedback in a hypothesis testing (HT) paradigm. Thirteen college students serially tested hypotheses concerning a hidden rule by judging its presence or absence in triplets of digits and revised them on the basis of an exogenous performance feedback. ERPs time-locked to performance feedback were then examined. The results showed differences between responses to positive and negative feedback at all cortical sites. Negative feedback, indicating incorrect performance, was associated to a negative deflection preceding a P300-like wave. Spatiotemporal principal component analysis (PCA) showed the interplay between early frontal components and later central and posterior ones. Lateralization of activity was selectively detectable at frontal sites, with a left frontal dominance for both positive and negative feedback. These results are discussed in terms of a proposed computational model of trial-to-trial feedback in HT in which the cognitive and emotive aspects of feedback are explicitly linked to putative mediating brain mechanisms. The properties of different feedback types and feedback-related deficits in depression are also discussed.

DANTALE: a new Danish speech material.

A new Danish speech material (DANTALE) for clinical and experimental speech audiometry is digitally recorded on compact disc (CD). The speech material is designed to meet present audiological requirements at Danish hearing centres. One channel of the CD contains the speech signals and the other a masking noise. The CD also contains various calibration signals recorded on both channels at the end of the CD. The speech material compromises: 1) Digit triplets for the measurement of speech reception threshold (SRT). 2) Lists of monosyllabic words for the measurement of discrimination score (DS) for adults, children and small children. The word lists for the adults are equalized with regard to important phonetic and "visual" elements and the word lists for the children consist of minimal pairs. 3) Continuous speech for the measurement of the most comfortable loudness level (MCL), assessment of hearing aid fitting and the like. The masking noise is an amplitude-modulated, speech-shaped noise signal, which is designed to simulate a 4-person speech babble in order to assess both the frequency selectivity and the temporal resolution. The speech material is described and the long-term power spectra and modulation spectra are given.

Imaginal Recoding of Numbers

Most mnemonic systems require subjects to use mental imagery of one form or another. For instance, the method of loci and the link method among others both rely on mental imagery in aiding recall. It has often been demonstrated that imagery facilitates recall ( 1 ) . If a method could be devised to recode digital information into visual images, there should be an increase in the number of digits later recalled relative to the number of digits recalled without such imaginal recoding. A mnemonic code was developed to recode digit triplets into visual images. The first digit in a triplet was recoded into an image of an animal, the second into an action and the third into an image of a place. Thereby each triplet was transformed into an image of a particular animal performing a certain action in a specified place. The code contained the words for 10 animals, 10 actions (verbs), and 10 places for the 10 digits in the three positions, respectively. Eight undergraduates were paid for their individual participation in the study. The first part of the procedure was a preliminary control free recall test of 15 random digit triplets. The triplets were presented separately for 8 sec. each with a 1-sec. inter-item interval. A cathode ray tube (Model ADM 3A) controlled by an ADS/1800E process control system was used to present items. The second part of the procedure involved subjects' participation in several code-learning sessions. All subjects were trained in the following manner: They learned separately by rote the three word-number lists, then they learned verbal encoding and decoding of the words and digits associated with each list, and finally, they practiced visualizing the animals performing actions in a place. Each session lasted about 1 hr., and an average of 7.88 sessions per subject occurred over five to nine days. Subjects were trained until a nine-second-per-triplet encoding criterion was met in about 6 to 7 hr. of training. Subjects also had to demonstrate they were using the code by describing some of the images they developed of each triplet in two practice tests prior to the final test. The final test was identical to the control test except that a different set of triplets was used and the subjects were instructed to use the imaginal recoding system and store the items in encoded form. At the time of recall they decoded the items into numbers. Different lists were used with different subjects. The mean number of triplets correctly recalled in the control and in the imaginal recoding conditions were 4.12 and 3.25, respectively. Performance was significantly better in the control condition than in the final test condition ( t , = 2.50, p < .05). The failure of the imaginal recoding to increase recall is consistent with the finding that imagery instructions per se do not increase recall ( 2 ) . A more precise delimitation of conditions of effectiveness of imagery is necessary.

Limited Magic of Binary-to-Octal Recoding and Memory Span

The purpose of this study was to verify the effect of binary-to-octal recoding on memory span. Four experimental conditions were used: (1) all-binary condition consisting of lists of triplets of binary digits where binary digits were used as input and output in a memory span task; (2) binary-octal-binary condition in which the subject encoded binary triplets into octal digits, retained octal digits and at the time of recall decoded octal digits back into binary triplets; (3) binary-octal-octal condition in which the subject encoded the presented binary triplets into octal digits and at the time of recall reproduced the material in the encoded octal form; and (4) all octal condition with octal digits used as input and output in the same memory span task. Memory span was determined for all conditions in terms of octal digits or the corresponding binary triplets. Three subjects were tested repeatedly in all of the four conditions in a block-randomized order after having learned the binary-to-octal code. Results yielded significant increase in memory span in all three subjects when decoding at recall was not required and significant increase in memory span in two subjects when decoding was required in recall. The increase in memory span due to recoding was moderate and far less dramatic than predicted by constant-chunk hypothesis.