Ten amnesic patients aged 42 to 69 with a mean age of 58 were selected. There were eight men and two women. Six of the patients were amnesic following a history of alcohol abuse ("Korsakoff" amnesics), two were amnesic following a viral infection (encephalitis), and two had suffered accidental head injury. The normal Control group consisted of ten undergraduate students (five male, five female) who took part in the study as a course requirement.
In the motor learning task, participants copied the experimenter as she went through a series of 20 actions with a set of everyday objects (e.g., breaking a match). There was a three minute interval after the last action.
Subjects were then shown 20 sheets of paper, on each of which were depicted three actions. Their task was to choose for each sheet which of the three actions had earlier been performed by the experimenter and copied by themselves.
The motor learning task was followed by the verbal learning task. In the verbal learning task the experimenter read aloud a list of 20 words at a rate of one every two seconds. Subjects were told to try to memorise the words. Subjects were asked to recall the words after a one minute interval.
The data for each participant on the two tasks are shown in Table 1.
Table 1: Scores out of 20 for the amnesic and normal Controls on action recognition and word recall.
| Task | ||
|---|---|---|
| Action Recognition | Word Recall | |
| Amnesics | ||
| S. 1 | 20 | 8 |
| 2 | 17 | 7 |
| 3 | 18 | 6 |
| 4 | 8 | 17 |
| 5 | 19 | 5 |
| 6 | 20 | 4 |
| 7 | 10 | 18 |
| 8 | 20 | 3 |
| 9 | 19 | 7 |
| 10 | 10 | 9 |
| Mean | 16.1 | 8.4 |
| Controls | ||
| S. 1 | 19 | 20 |
| 2 | 16 | 18 |
| 3 | 17 | 19 |
| 4 | 18 | 15 |
| 5 | 20 | 15 |
| 6 | 20 | 20 |
| 7 | 19 | 12 |
| 8 | 20 | 16 |
| 9 | 19 | 20 |
| 10 | 18 | 20 |
| Mean | 18.6 | 17.5 |
t-tests for matched samples were carried out comparing performance on the verbal task and the motor task separately for the Amnesics and the Controls. The Amnesics were significantly worse on the verbal task than on the motor task (t = 2.54, df = 9, p < .05) whereas for the normal Controls the comparison was not significant (t = 1.04, df = 9).
It is concluded that this kind of brain damage has no effect on motor learning skills but does affect verbal learning.
The control participants are generally younger than the Amnesics. It is thus possible that poor word recall in the Amnesics is due to age related deficits rather than to the brain damage described above. To test this hypothesis, correlations were computed between the participants' age and word recall score. For the ten participants in this Control group the Pearson product-moment correlation (r) is .15, for the ten Amnesics it is .59. Neither of these correlations is significant. Therefore, it is concluded that the difference in mean age between the Amnesic and Control group cannot account for the poor word recall scores of the former group.