Table 2.
Dichotic Listening Task Performance for Schizophrenia Patients, First-Degree Relatives of Schizophrenia Patients, and Nonpsychiatric Control Groups.
| Task | Patients | Relatives | Controls | Test Value | p Value1 |
|---|---|---|---|---|---|
|
|
|
|
|||
| n=19 Mean (SD) |
n=37 Mean (SD) |
n=36 Mean (SD) |
|||
| Accuracy: Number of Correct Targets2 | |||||
| High Tones | 38.32 (3.42) | 39.54 (1.10) | 39.25 (1.66) | F(2,89)=2.5 | .09 |
| Low Tones | 32.78 (6.72)a,b | 38.28 (2.08) | 36.78 (5.05) | F(2,89)=8.8 | <.001 |
| Total | 71.06 (8.28)a,b | 77.81 (2.56) | 76.03 (5.83) | F(2,89)=9.3 | <.001 |
| Target Detection: d′ | |||||
| High Tones | 4.45 (.65) | 4.65 (.42) | 4.63 (.53) | F(2,89)=1.0 | n.s. |
| Low Tones | 3.73 (.79)a,b | 4.53 (.47) | 4.41 (.70) | F(2,89)=9.8 | <.001 |
| Total | 4.09 (.58)a,b | 4.59 (.33) | 4.52 (.53) | F(2,89)=6.9 | .002 |
| Response Threshold:β | |||||
| High Tones | .96 (.06)b | .98 (.02) | .98 (.03) | F(2,89)=2.9 | .06 |
| Low Tones | .87 (.10)a,b | .96 (.04) | .94 (.08) | F(2,89)=8.5 | <.001 |
| Total | .91 (.07)a,b | .97 (.02) | .96 (.05) | F(2,89)=9.3 | <.000 |
| Reaction Time for Targets: (msec) | |||||
| High Tones | 408 (139) | 369 (88) | 362 (69) | F(2,89)=1.6 | n.s. |
| Low Tones | 508 (121)a,b | 434 (92) | 440 (85) | F(2,89)=4.0 | .02 |
| Total | 460 (127)a,b | 399 (86) | 401 (73) | F(2,89)=3.1 | .05 |
Note. SD=Standard Deviation. A correction factor was used in computing d′ in cases of a perfect hit rate (1.0) or false-alarm rate (0.0) to allow for unbiased estimation of d′. A two-way ANOVA of d′ with group (patients, relatives, and controls) and trial type (high tones: 2400 Hz and 1600 Hz collapsed across attended side; low tones 1200 Hz and 800 Hz collapsed across attended side) revealed main effects for trial type, F(2,89) =20.16, p < .0001 and a group-by-trial type interaction, F(2,89)=4.84, p=.01. A similar two-way ANOVA of β yielded a main effect of trial type, F(2,89) =45.10, p < .0001 and a group-by-trial type interaction, F(2,89)=4.71, p < .05. Subjects responded faster to the high tone pairs of tones as compared to low tone pairs, F(1,89)=180.48, p<.0005.
Denotes significance level of Oneway ANOVA for specified set of trials.
Total number of targets presented at each tone was 40.
Schizophrenia Patients < Nonpsychiatric Controls,
Schizophrenia Patients < Relatives of Schizophrenia Patients.