An investigation of errorless learning in memory-impaired patients: improving the technique and clarifying theory

Abstract

In rehabilitating individuals who demonstrate severe memory impairment, errorless learning techniques have proven particularly effective. Prevention of errors during acquisition of information leads to better memory than does learning under errorful conditions. This paper presents results of a study investigating errorless learning in three patient groups: those demonstrating mild, moderate, and severe memory impairments. The first goal of the study was to trial a new version of errorless learning, one encouraging more active participation in learning by patients via the use of elaboration and self-generation. This technique led to significantly better memory performance than seen under standard errorless conditions. This finding highlights the value of encouraging active and meaningful involvement by patients in errorless learning, to build upon the benefits flowing from error prevention. A second goal of the study was to clarify the mechanisms underlying errorless learning. Memory performance under errorless and errorful conditions was compared within and across each group of patients, to facilitate theoretical insight into the memory processes underlying performance. The pattern of results observed was equivocal. The data most strongly supported the hypothesis that the benefits seen under errorless learning reflect the operation of residual explicit memory processes, however a concurrent role for implicit memory processes was not ruled out.

Introduction

One of the more successful techniques used in rehabilitating people with memory disorders, especially those with more severe forms of impairment, is errorless (EL) learning. The EL learning technique involves learning or encoding new information without error. To achieve this, individuals are given the correct information during each learning episode. In a typical experiment, this involves the examiner providing the same new information to the patient over multiple learning trials, with the patient repeating or writing down the information. This can be contrasted with errorful (EF) learning, where individuals are encouraged to guess and thus are more likely to produce errors during learning [1], [2]. Despite some successes, the EL learning technique is not without limitations. For patients with severe memory impairment, acquisition is effortful and requires the therapist or examiner to direct learning. There also appears to be little generalisability across learning situations. If the effectiveness of the technique is to be enhanced, there are two issues that need to be addressed. The first is the reliance on the examiner to generate responses. If individuals can generate their own responses, this in turn may strengthen memory traces and perhaps facilitate the process. Secondly, theoretical implications need to be clarified. Presently, questions remain about the processes responsible for improved memory under EL learning conditions. If the mechanisms that support such learning are clearly identified, we will be in a better position to improve the effectiveness of the technique. Both issues are addressed in the present research.

EL learning originated in behavioural psychology research in the 1960s. Terrace [3], [4] and Sidman and Stoddard [5] used a similar technique to teach visual discrimination to pigeons and to children with intellectual disabilities. Although new learning was poor in both groups, it was found that training under errorless conditions facilitated learning in these populations. However, the general technique was not applied to the treatment of memory disorders until the 1990s. The focus of this work was both practical and theoretical. Researchers investigated both the effectiveness of the technique and the mechanisms or processes that supported learning when applying the technique.

EL learning was first applied to the treatment of memory disorders by Wilson et al. [1]. These researchers investigated list-learning performance in severely memory-impaired (i.e. amnesic) patients and two non-impaired control groups (a young group and an elderly group). They found that patients made significantly more correct responses on a cued recall test following EL learning than they did following EF learning. Furthermore, the amnesic group received greater benefit from the EL condition than did either control group. Baddeley and Wilson [2] argued subsequently that EL learning both enhanced learning and reduced forgetting rates in amnesic patients.

Many researchers have replicated this finding of superior performance under EL learning conditions both in immediate and delayed memory tests. The EL technique has been shown to be effective when learning remotely linked word pairs and unrelated word pairs [6], as well as learning extended word lists [7]. It has also been useful in the acquisition of more practical information. In a series of case studies, amnesic patients showed superior learning of object names, names of people, word lists, orientation items (time, place, age) and general knowledge, as well as electronic diary programming [1]. A recent study found a limited advantage of EL over EF methods on a face-name learning task [8]. EL learning has also been applied to the restoration of premorbid knowledge [9] and the development of procedural skills in a work setting [10]. Although most studies have focused on amnesic patients, the EL learning technique has also been shown to be reasonably successful in facilitating performance in patients suffering from a moderate degree of memory impairment [7].

Despite these benefits, there are limitations to the usefulness of the EL technique. First, not all studies have found the benefits of EL learning to be maintained over time delay (e.g. [6]). Furthermore, there is some evidence to suggest that EL learning may not be the best method in all cases, particularly when acquiring more complex information. For instance, tasks involving multiple steps or requiring the acquisition of more detailed information have been difficult for amnesic patients even when learning under EL conditions. Evans et al. [8] found only a limited advantage of EL over EF methods on a face-name learning task, and no advantage on other complex tasks, namely, programming an electronic organiser and route-finding.

A further limitation of the EL learning technique is that it remains quite directive. Participants need only listen to correct answers, follow written instruction, or on occasion write the answer, over a series of learning trials. Wilson and her colleagues have suggested that this may not be sufficient to ensure adequate learning [1]. This raises an interesting question—could the effectiveness of the EL learning technique be improved if patients were somehow able to generate their own correct responses during learning?

There is existing evidence to suggest the EL learning technique can be improved. Although Evans et al. [8] found a limited advantage when learning face-name associations using standard EL conditions, memory performance was best when the EL learning task was extended to include active processing of associations via use of a visual imagery strategy. Further evidence is provided by Squires et al. [6], who found that the benefits of EL over EF methods were greater on a novel association task when compared with remotely linked word pairs. These researchers argued the added cognitive effort required during learning of novel associations, involving the creation of an extrinsic link between the target words, resulted in a stronger memory representation and better performance at test.

Additional evidence from the cognitive literature is relevant to this point. Much of the evidence concerning the benefits of active participation in learning comes from research investigating levels of processing (LOP) theory. In LOP theory it is argued that the strength or durability of a memory representation is dependent on the manner in which the information is processed during encoding [11], [12]. Memories are strengthened by elaboration, or by processing information on the basis of its meaning. Current EL learning techniques are akin to rote learning, as they involve repeated exposure to correct information. According to LOP theory, retention of information acquired during EL learning should be improved by increasing the level of active involvement or processing engaged by participants during encoding. Researchers have shown memory performance is best when information is learned in a meaningful or semantic context—for instance, when processed conceptually or elaboratively rather than on the basis of superficial or lexical characteristics. This finding has emerged in both clinical (e.g. [13], [14], [15]) and non-clinical (e.g. [11]) populations. This evidence highlights the value of exploiting semantic memory, which is preserved in many people with acquired memory deficits. The present research draws upon this notion, and seeks to determine whether EL learning can be improved by encouraging participants to engage in elaborative processing during learning.

There is considerable evidence supporting the case that EL learning is an effective technique for the rehabilitation of patients with memory impairment. Yet the cognitive processes responsible for improved retention of information learned under EL conditions are the subject of some debate. Two theories have been proposed, and both focus on the distinction between implicit and explicit memory. The first theory proposes that the benefits seen under EL conditions are supported by implicit memory. The second theory proposes that these benefits are supported by residual explicit memory.

The implicit memory theory was first proposed by Baddeley and Wilson [2] to account for the facilitation in memory performance observed in amnesic patients who were subjected to the EL learning technique. This theoretical account is not surprising given evidence of preserved implicit memory in these patients [16], [17]. Specifically, Baddeley and Wilson found that under EF conditions, amnesic patients tended to repeat the same errors across learning trials. It was suggested this occurred because EF learning relies on explicit memory processes, which amnesic patients cannot apply. Explicit processes enable the conscious monitoring and elimination of errors. Without this capacity, one cannot modify and update responses during learning. Hence, under EF conditions any error generated by memory-impaired patients may be repeated, resulting in reinforcement of an incorrect response. In contrast, implicit memory, attuned to eliciting production of the strongest response, is reported to be intact in amnesic patients (e.g. [16], [17]. Implicit learning is well served under EL conditions, as by eliminating errors during learning the strongest response will be the correct response and this would be the only one reinforced. On the strength of these arguments and their findings, Baddeley and Wilson concluded that the advantages seen under the EL technique reflected the operation of implicit memory.

Further, albeit limited, support for the implicit theory was provided by Evans et al. [8]. These authors concluded that EL learning may only be beneficial in tests of implicit memory, and may be ineffective when explicit recall of information is required. They report mixed results in their study, and argued that EL learning was only useful in tasks or situations facilitating retrieval of implicit memory for learned material.

Critical analysis of the above studies exposes some shortcomings. For instance, although Baddeley and Wilson [2] proposed that EL learning must be supported by implicit memory, this conclusion was based on the assumption that implicit memory was preserved in patients with amnesia. Although numerous researchers have found that implicit memory and learning is relatively preserved in amnesia [16], [17], other researchers have argued that implicit memory is not preserved in all tasks performed by amnesic patients [18]. This highlights the need to demonstrate preservation of implicit memory with the task being used, rather than simply accepting an assumption that may be false. The reasoning behind Evans et al.’s [8] explanation is also open to question. These authors concluded that EL learning may only be beneficial in implicit memory tests. Yet in their study (as in most others) EL learning was beneficial in cued recall tasks, and in one free recall task. Both cued and free recall are measures commonly employed to tap explicit memory.

A subsequent line of empirical research provided support for an alternative theory—namely, that the benefits observed during EL learning are supported by residual explicit memory. This was first suggested by Hunkin et al. [7]. These researchers used the same learning procedure as Baddeley and Wilson [2], but tested memory in two ways—using an implicit test (fragment completion) followed by an explicit test (cued recall). They found no correlation between items produced in the implicit and explicit memory tests, which is contrary to expectations if performance in cued recall reflects implicit memory. Based on these findings, Hunkin and colleagues argued that the benefits associated with EL learning must therefore reflect the operation of residual explicit memory. This conclusion was strengthened by their findings of EL learning advantages in free recall—a task that is arguably explicit. They thus joined other researchers who argue that any learning observed in amnesia is only possible via the use of residual explicit memory (e.g. [19]).

Evidence supporting this second theory is also open to qualification. In the Hunkin et al. [7] study, the accuracy observed in performance in the fragment completion task was quite low. Performance at such low rates of accuracy might be considered to reflect residual explicit memory, which is expected to be poor in groups with severe memory impairment. Yet this conclusion poses some difficulties, given the lack of correlation with performance on cued recall (their test of explicit memory). The authors note their failure to find a correlation between implicit and explicit test performance may be an artefact resulting from the use of different stimulus materials in their tasks. Performance in fragment completion (i.e. implicit test) was compared with that on word-stem completion (i.e. explicit test) and the processes involved in completing these tasks may differ.

In sum, error prevention during learning has been found in many cases to be advantageous over techniques that allow errors to be made in the study period. The benefits of EL learning have been shown in a number of learning tasks using a variety of materials and information. To date, two theories have been proposed to explain the mechanisms underlying this observed advantage. However the evidence provided to date in support of each theory remains open to challenge. The present research re-examines both theories and attempts to establish which best fits the data.