Robert S.P. Jones a

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Robert S.P. Jones a n d C B . Eayrs
University College of North Wales, Bangor, Gwynedd, LL57 2DG

Abstract The use of procedures which minimise the making of errors
is a popular method of teaching skills to people with learning disability.
The origin of this approach can be traced t o two distinct sources: the
work of B.F. Skinner on programmed learning, and the work of H.S.
Terrace on discrimination learning. This early work is reviewed and
research findings which highlight the negative side affects of an
‘errorless’ approach are discussed. The role of prompting, attention,
reinforcement and generalisation is outlined. Recommendations for the
development of teaching programmes are made.


One of the most fundamental aspects of skill acquisition involves the
development of stimulus control. It can be argued that the ability of an
organism to discriminate between stimuli with which it is presented
represents the most basic foundation of learning. The acquisition of an
operant discrimination has been defined as the process whereby an
organism comes to respond more frequently to a stimulus correlated with
reinforcement, S + , than to a stimulus associated with non-reinforcement,
S – (Terrace, 1963a).

Historically, the learning of an operant discrimination involved the
differential reinforcement of responses which occurred in the presence of the
S + and the extinction of responses which occurred in the presence of S – .
This procedure is most commonly known as ‘trial-and-error’ learning with
any response in the presence of S- being regarded as an error. The making of
errors in acquiring a discrimination was not only therefore extremely
common in the development of stimulus control but it was frequently
assumed that the making of errors was an essential occurrence if an organism
was to master a discrimination (e.g. Keller & Schoenfeld, 1950).

09.52-9608/92/02 0204-9 $01.80/0


0 1992 R . Jones & C. Eayrs
Vo1.5, No.2, 1992


In applied work with people with learning disabilities, discrimination
learning using trial-and-error methods was limited by a number of factors
which involved the making of mistakes or errors. It was felt that for some
people with a learning disability the demands of learning by trial and error
could provoke problem behaviours (Carr, Newsom & Binkoff, 1980; Weeks
& Gaylord-Ross, 1981). Problems such as ‘apathy, aggression, self-injury,
negativism and tantrumming’ have been cited as direct consequences of the
trial-and-error learning approach (Touchette & Howard, 1984; Hamblin et
a/. ,197 1).

In the early 1960s H.S. Terrace conducted a series of now famous animal
experiments which suggested that not only was the making of errors
unnecessary in the development of learning but that learning was actually
facilitated if no errors were made during the acquisition of the
discrimination (Terrace, 1963a, 1963b,; 1964; 1966). Essentially Terrace’s
early work involved the use of trial and error procedure designed to teach
pigeons to peck a key illuminated with a red light but not to peck a key
illuminated with a green light. When the pigeons pecked the red stimulus
( S + ) they received a food pellet and when they pecked the green stimulus
(S – ), nothing happened. Both keys were present at the same illumination
during the experiment. A second group of pigeons began the experiment
with the green key dark and had the light behind it slowly ‘faded in’ during
the training condition. By the end of the experiment the second group also
had two illuminated keys of equal intensity present. The second group made
very few responses to the green light. Indeed it was as if they hadn’t noticed
its presence. The stimulus fading procedure (resulting in few, if any,
responses being made to the S – ) was called errorless learning.

Although Terrace’s work has not led to major changes in the theoretical
explanations of discrimination learning (Robinson & Storm, 1978), this
early work stimulated subsequent research which has had a major effect on
strategies for teaching people with learning disabilities.

In the years immediately following Terrace’s early work, errorless
procedures were employed in teaching simple discriminations to children
with learning disabilities (e.g. Sidman & Stoddard, 1966, 1967; Touchette,
1968). This work, supported Terrace’s claim that discrimination learning
was facilitated by the use of errorless learning techniques. Perhaps the
major impact of this work, however, was the finding that children with
learning disabilities could be taught by errorless teaching methods in cases
where such discriminations could not be acquired by traditional trial-and-
error techniques (Walsh, 1985).

Another influence on ‘errorless’ teaching technology came from
Skinner’s pioneering research on applied behaviour analysis and


programmed learning (Skinner, 1968). This research suggested that errors
could be avoided by breaking tasks down into small steps, by the use of
shaping through successive approximations and by the optimal spacing of

As a result of these influences, the errorless learning approach was
quickly extended beyond basic discrimination training to encompass a
complete technology of teaching covering areas far removed from Terrace’s
original work. An emphasis on an ‘errorless’ approach to teaching people
with learning disabilities became increasingly popular and to this day many
books and training manuals owe their origin, overtly or covertly, to this
approach (Best, 1987; Donnellan, La Vigna, Negri-Shoultz & Fassbender,
1988; Foxen & McBrien, 1981; La Vigna & Donnellan, 1986; Smith, 1990;
Zarkowska & Clements, 1988)

Although there can be little doubt that the influence of errorless learning
techniques on the training of people with learning disabilities has been of
great benefit, a number of problems exist with this approach.

Difficulties with Errorless Learning

Narrowing of attention

Conclusions from a number of studies have suggested that as early as
1966 some researchers were questioning the efficacy of errorless techniques
in certain situations (cf. Walsh, 1985).

The major conclusions from those studies suggest that fading techniques
may confine the person’s attention to very narrow attributes of the stimulus
associated with reinforcement (S + ). Richell, for example, questioned the
adaptability of a person who had been trained through errorless procedures
and particularly the ability to cope in new situations where errors would
occur (Richell, 1966). Bijou & Baer (1966) also questioned the ability to
transfer skills to other settings. Both of these researchers made these
suggestions on theoretical grounds.

In 1968, however, Gollin & Savoy conducted a series of experiments
which provided experimental evidence for the assertion that in some
situations errorless learning may result in a greater number of mistakes
compared to trial and error learning once transfer of learning to a new
situation is involved. Gollin & Savoy (1968) divided a sample of 52 children
into two groups. Both groups were taught a discrimination task followed
by a conditional discrimination task (where the nature of the response is
dependent on the nature of the discriminative stimulus). One group was
taught by a trial-and-error procedure and one by using an errorless fading


technique. Although more children who were trained by the fading
procedure performed without errors during training, more children in the
trial-and-error group solved the conditional discrimination problem. Thus,
it appeared that for simple discriminations requiring a single response to a
stimulus, errorless methods resulted in fewer errors. When the task became
more complicated, however, with the use of a conditional discrimination
task then the errorless group did not perform as well.

Similar findings have been reported by a number of authors, (e.g. Wolfe
& Cuvo, 1978; Walsh, 1985). Walsh (1985) compared errorless and trial-
and-error procedures o n a conditional discrimination test. The results of
Walsh’s (1985) study were similar to those of Gollin & Savoy (1968). Again
errorless learning techniques worked very well when the task was a very
simple one requiring only a simple response. When the task became more
complicated and necessitated paying attention to more than one stimulus,
then errorless learning proved to be an inferior teaching technique when
compared with trial-and-error learning. Walsh concluded that ‘under
certain conditions fading techniques are not able to provide optimal
conditions for learning a given task’ (Walsh, 1985:36).

It appears therefore, that access to a combination of both S + and S –
throughout training is important in all but the most simple discrimination

New responses

In situations where a completely new response was required (as opposed
to strengthening an existing behaviour) it was assumed that the optimum
mechanism for generating the new response was the prompting of that
response and the gradual fading of the prompt as the behaviour became
established. No direct experimental evidence was obtained which indicated
that this method was, in fact, the optimum means of generating new
responses. Rather, this appears to have been an intuitive ‘common sense’
decision and it is possible that the emphasis placed on avoiding errors in
accounting-for successful teaching, and the consequent generalisation of the
methodology, might be misplaced.

Although the work of Skinner (1968) is perhaps the most relevant to the
operant teaching of new skills, the term ‘errorless’ has been traditionally
applied to the work of Terrace rather than Skinner. The danger here is that
this confusion could lead to the assumption that the methodology which is
appropriate for teaching pigeons to peck red rather than green illuminated
keys will also be appropriate for teaching self-care skills to people with a
learning disability. A closer examination of the procedures used, however,


reveal a number of factors, apart from ‘errorlessness’ which could account
for success or failure.

In the typical two choice discrimination procedure, the animal or person
typically makes a simple ‘pointing’ response. This may either be a pecking
response (Terrace, 1963a) or a gestural indication (Cullen, 1978). The
prompt to respond is the actual stimulus which is designed to gain control
over the behaviour once learning has taken place. Furthermore, at some
level a choice is being made from the outset. This can be conceived of as
a trial-and-error scenario with the dice loaded towards success.

When this procedure is compared with the use of ‘errorless’ procedures
to teach self-help skills to people with learning disability a number of
differences become apparent. Firstly, the motor behaviour is frequently far
more complex than simply ‘pointing’ (e.g. brushing teeth, feeding with a
spoon). Secondly, the form that the prompting takes is different. The
avoidance of errors is achieved by the physical prompting of movement by
the trainer. The person has no choice about what he/she does. At its
extreme, the person may be so passive in the procedure that he/she may
initially be little more than an extension of the trainer’s own musculature.
Thirdly, the discriminative stimuli during training are not always the same
as those which are t o gain final control at the end of the training procedure.
For example, the final discriminative stimulus for handwashing would
normally be the presence of dirt. During training, however, it is the presence
of the trainer, and the use of a prompting procedure which acts as a
discriminative stimulus. It is these aspects of the training procedure which
are so difficult to ‘fade out’. Fourthly, in Terrace’s errorless discrimination
learning procedure the S + remained constant throughout whilst S – was
‘faded in’. In the self-help skills teaching situation, however, S +
continually changes as prompts are ‘faded out’. Thus, it may be an
oversimplification to simply compare errorless versus trial-and-error
training unless these other aspects of the environment are controlled.


A further disadvantage with the errorless approach seems to lie in the
area of generalisation. As was mentioned earlier, many errorlessly trained
discriminations require a prompting component. In such cases, the person’s
ability to generalise a learned skill is wholly dependent on the success with
which the prompting component can be gradually withdrawn or faded out.
Unfortunately, ‘it is often the case that students who respond appropriately
when prompted founder when the prompt is removed’. (Touchette &
Howard, 1984:175). In practice, the fading of prompts is a


very difficult part of teaching. Premature removal of prompts can lead to
persistent incorrect response patterns which preclude acquisition of the
target repertoire (Sidman & Stoddard, 1966; Touchette, 1968). If, on the
other hand, prompts are presented for an unnecessarily extended period
then the person may become dependent on the prompt. Either of these
extremes will preclude successful generalisation of learning to novel
situations. It is, nevertheless, all too common t o find that a person with a
learning disability can only display a learned skill with the aid of a prompt,
despite many unsuccessful attempts to fade out prompting. As Touchette
& Howard (1984) have said ‘. . . research has not yet resolved the question
of how to produce a successful transfer from prompted to unprompted
responding’ (p. 175).


One of the major advantages of an errorless approach lies in the high
frequency of reinforcement available to the person. In teaching people with
a learning disability many authors (e.g. Foxen & McBrien, 1981), have
advocated that each prompted response should be followed by
reinforcement. This continuous reinforcement (CRF) schedule, however, is
unlikely to lead to spontaneous generalisation to new situations. There
exists a wide variety of research data which suggests that once continuous
reinforcement is withdrawn, the acquired behaviour quickly extinguishes
(Kazdin & Polster, 1973; Koegel & Rincover, 1977; Kazdin, 1984).
Although it has been advocated that, as soon as a behaviour is acquired on
a CRF schedule, reinforcement should be switched to an intermittent
schedule, there have been a number of difficulties with this procedure
(Tierney & Smith 1988; Dehn, 1969). Dehn (1969) found that the
smoothness of transfer from continuous to intermittent schedules is a key
factor in the success of the procedure. Hamblin et al. (1971) in discussing
this work, concluded that ‘after acquisition during the transition from
continuous to intermittent reinforcement, negative behaviour is increased in
proportion t o the haste with which the transition is made’ (p. 153).

Research carried out with children with learning disabilities (Tierney &
Smith, 1988), demonstrated that responding on an intermittent schedule
during the maintenance phase of a training programme was more likely if
initial response acquisition was programmed using a partial schedule than
if response acquisition was initially programmed using a CRF schedule and
then switched t o an intermittent schedule (Tierney & Smith, 1988). This
suggests that even from the beginnings of teaching a discrimination, not all
correct responses should be reinforced if optimal response generalisation is


to be attained. Clearly, this would mean that one of the major aspects asso-
ciated with an errorless approach (each response is correct and leads to rein-
forcement) could not occur. A dilemma between speed of initial response
acquisition and optimum generalisation of responding could thus be

A further issue with regard to reinforcement and subsequent
generalisation involves the timing of reinforcement administration. It is
frequently assumed that the time delay between responding and contingent
reinforcement should be as short as possible and this is usually advocated
in teaching materials (e.g. Foxen & McBrien, 1981). In the natural
environment, however, there is often a delay between responding and
reinforcement and it has been suggested that such a delay may actually
facilitate generalisation (Kazdin, 1982).


In summary, although errorless learning has undoubtedly provided a
technology of teaching which has led to significant advances in the
education of people with a learning disability, a number of difficulties
remain with this approach. Firstly, fading techniques appear to result in a
narrowing of attention which may inhibit the subsequent learning of more
complex behaviours. Secondly, where errorless prompting procedures are
used, difficulties may arise in the removal of the prompts due to an
overdependence on their availability. Thirdly, and perhaps most
importantly, there are difficulties with the subsequent maintainence and
generalisation of behaviours acquired through errorless methods.


While the literature clearly points out that a learned discrimination can
be achieved and maintained by specifying the setting conditions (prompts)
and locating the maintaining events in the natural environment, it is
suggested that prompting should be as infrequent as possible and that where
possible the learner should have access to a wide range of stimuli in addition
to the S + . It can be argued that errorless learning methods should only by
used in situations where trial-and-error methods have proven unsuccessful.
The preferred treatment approach should be the shaping of the desired
response, by successive approximations in the natural environment. Thus,
an attempt should be made to teach using trial-and-error methods in the
first instance before fading procedures are employed.


Once the decision to use errorless methods has been made, specific
strategies need to be incorporated to take account of prompting, attention,
reinforcement and generalisation.

Preventing errors at all costs does not seem to merit the same emphasis
that Terrace’s early work might suggest. In particular, it is not
recommended that overprompting is used t o avoid making mistakes. In
terms of subsequent generalisation, it is probably more advantageous for
a client to make a mistake in mastering a discrimination than to become
dependent on prompting. Each individual, whatever his o r her degree of
learning difficulty, brings a unique constellation of skills, experience, and
talent t o any new learning situation. It is important to adapt all teaching
t o be as flexible and individualistic as possible and not to attempt to fit the
learner into a predetermined system of training o r instruction.


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