PRUEBA DE HIPÓTESIS

Experiments investigating the relationship between emotion and recall are based on

the associative network theory (Anderson, Bower & , 1973; Bower, 1981) described

above. Generally speaking the theory postulates two effects:

State dependent learning is the tendency for material to be recalled best when conditions at recall match those of the encoding of the data. Experimental evidence

supporting this hypothesis has been gathered from several investigations (see review

by Blaney 1986), but contradicting results have also been demonstrated. Although

Bower himself reported successful results in 1978, when a group of subjects encoded

data under induced mood, and recalled better after induction of matching mood, he

failed to replicate these findings in 1985 (Bower, et al., 1985; Bower, et al., 1978).

Nonetheless, other experiments have shown some support for the notion of state

1984).

Mood congruity effects depend on similarity between the subjects mood and the

material to be recalled, with the hypothesis that negative mood will result in better

recall for negative information and vice versa. Blaney (1986) reviewed over 30

studies and concluded that indeed there appears to be superior recall for mood

congruent material. For example, Teasdale (Teasdale, Taylor & Fogarty, 1980)

demonstrated that induced negative mood resulted in bias towards mood congruent

autobiographical memories. However, there is evidence to suggest that another factor

might be operating to mediate the effect; evidence shows that people have a recall

bias towards material which is closely associated with their self-concept (Clark &

Teasdale, 1985; Isen, et al., 1978; Teasdale & Russel, 1983b), and the congruity effect

might be strengthened through such an association. This would mean that the more

negative the self-concept the more the tendency to recall negative material associated

with the self, but not necessarily accompanied by a tendency to recall more negative

material associated with others.

Recall bias for negative material in depressed groups has been demonstrated by

several experiments. Blaney (1986) found both mildly depressed students and

clinically depressed groups to be more likely to recall negative material than positive

or neutral material, as opposed to control groups that show an opposite trend, towards

positive material. This effect is most pronounced when subjects are asked to focus

on the applicability of the material to themselves, at the encoding stage, by, say,

led Mathews and Bradley (Mathews, et al., 1983) to manipulate the encoding stage

further, so that subject learnt the stimuli in two conditions, once in relation to

themselves and once in relation to others. The results show a bias for negative

material only in the self-reference condition, giving some credence to the idea of a

self-schema operating to mediate recall. Lloyd and Lishman (Lloyd & Lishman,

1975) found depressed patients faster to recall unpleasant memories, and the bias

appeared in direct relationship with the severity of their pathology. The results of

other experiments involving memory of past experiences in depressed groups

(Teasdale & Fogarty, 1979; Teasdale, et al., 1980; Clark & Teasdale, 1982) show a

robust effect both when recall is spontaneous and when directed. However, the bias

for learning certain words better than others appearing in a list shows more ambiguous

results; Breslow et al., (Breslow, Kocsis & Belkin, 1981) demonstrated that depressed

groups learnt less positive words, but showed no preference for learning negative ones.

McDowell (McDowell, 1984) replicated these finding using mixed lists, and separate

ones for positive and negative words, and found the effect only in the mixed list

condition. This could be explained possibly as a result of competition for resources.

Although it is not inconceivable that depressed subjects show a recall bias towards

negative memories simply because they have been exposed to more of these than the

average person, this argument is challenged by the evidence arising from experiments

using induced moods, and from evidence for the bias being specific to self referential

encoding.

generally failed to show this bias (Mathews, et al., 1985), but conflicting evidence

exists to suggest that the effect might take place in certain circumstances; Nunn,

Stevenson and Whalan (Nunn, Stevenson & Whalan, 1984) demonstrated that

agoraphobic patients recalled more passages with agoraphobia related words (e.s.,

’Street’) than controls, and Martin et al (Clark, et al., 1983) showed high trait anxiety

subjects to be associated with better recall of negative self-referential words. Chronic

pain patients have been shown to recall more pain related words than neutral ones

(Pearce, et al., 1990; Edwards & Pearce, 1992). Chapter 4 attempts to establish

whether this recall bias is specific to self-reference or a general bias, and to eliminate

the possibility of a frequency effect confounding the results. The latter would mean

that results are due to exposure to pain words, resulting in a decreased threshold

needed for activation during search procedures. Chapter 5 investigates implicit and

explicit recall in pain patients, in an attempt to demonstrate independence between

integration and elaboration in pain patients. Chapter 6 investigates the specificity of

the recall bias; could it be attributed to high depression levels in pain patients, and if

so, do these patients demonstrate a recall bias towards depression related stimuli?