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Investigating reinforcement in altering response-times to reward, punishment and neutral stimuli, and the role of individual differences

Ethics Approval: 2012/031

Researcher: Alison Mackenzie

Supervisors: Dr Helen Davis and Dr Jon Prince

Honours Study Completed: 2012

The overall aim of this study was to investigate whether reward and punishment sensitivities could be associated with traits relevant to depression, and whether reinforcement (in the form of prizes) could influence those sensitivities, and indirectly, affect.

Unexpectedly, study one found that approach responses did not change between reward, punishment and neutral conditions, contrary to Hardin et al. (2006) who argued that contingency influence response times (RT). The expectations that the high negative-affect group would be significantly slower overall than the low negative-affect group were borne out. This is supports prior research demonstrating that negative-affect slows overall RT (Seligman, 1975). Overall, results indicated that affect is a more reliable indicator of approach speeds than what the participant was being asked to approach. No difference was noted between the control and intervention groups when asked to withdraw from punishment at baseline, contrary to work suggesting that high negative-affect groups would be faster to withdraw than the low negative-affect group (Kanter et al., 2008; Jacobson et al., 2001). The intervention group in study two neither demonstrated the expected acceleration on their approach to reward, nor a deceleration in their withdrawal from punishment speeds, after intervention. These particular results are contrary to suggestions that the relative presence/magnitude of a response is directly related the relative presence of environmental reinforcers and punishers for those responses (Herrnstein, 1970). Given the lack of change in RT and neuroticism scores, it is important to note that the affect scores did not change. This implies that the relationship between behaviour and neuroticism may well alter affect scores, but was not demonstrated here.

There are several limitations of the present research. For study one, as already noted, the rewards and punishments were not tangible outcomes, which may have reduced their motivating ability and therefore the ability of the conditions to demonstrate an effect on RT. Furthermore, the sample size for study two was too small to perform sound statistical analyses. The second major problem with study two was that the reinforcers were likely to be insufficiently motivating. Hopefully, highlighting these limitations will enable further research to avoid similar problems when investigating how short-term behavioural interventions, in laboratory settings, may influence affect. Foremost would be the inclusion of a large sample size, and either tailoring rewards to the individual or simulate a more motivating token economy (where items are worth the same value as the tokens collected).

One of the major implications of these current studies is that more research is needed to determine if RT can be changed with reinforcement, and whether this can be generalized to measures of wider behaviours, personality and affect. Study two has been valuable in demonstrating that if RT does not change, then neither does affect, and the overall project has also served to highlight withdrawal/avoidance behaviours in mood disorder research. It is important to determine if interventions based around short laboratory sessions can work, in order to fully investigate the ideal of a shorter intervention for sufferers of depression. If it is possible to reinforce a person to become more determined and tenacious in their reward-seeking, it could have far-reaching implications. A potential application of the technique - if it can be improved - is in interventions for post-natally depressed mums. If these women can be reinforced for behaving in a more positive way towards their children, it may assist in a speedy recovery from the disorder, enhance their experience of motherhood and contribute to a positive environment for the child. Another possible application of the technique is in assisting those with depression to engage in employment seeking. The process of seeking employment is not always gratifying, yet it is the depressed population - that may benefit most from the structure of work-life - who may be the first to stop pursuing it, in the face of rejection. If depressed individuals can be reinforced for continuing their search for work and not withdrawing from it, it may help them achieve the benefits that work can supply to them.

References

Hardin, M. G., Perez-edgar, K., Guyer, A. E., Pine, D. S., Fox, N. A. & Ernst, M. (2006). Reward and punishment sensitivity in shy and non-shy adults: relations between social and motivated behavior. Personality and Individual Differences, 40, 699–711.
Herrnstein, R. J. (1970). On the law of effect. Journal of the Experimental Analysis of Behavior, 13, 243–266.
Jacobson, N.S., Martell, C. R. & Dimidjian, S. (2001). Behavioral activation for depression: returning to contextual roots. Clinical Psychology: Science and Practice, 8, 255–270.
Kanter, J. W., Manos, R. C., Busch, A. M. & Rusch, L.C. (2008). Making behavioral activation more behavioral. Behavior Modification, 32, 780-803.
Seligman, M. E. (1975). Helplessness: on depression, development, and death. A series of books in psychology. San Francisco: W. H. Freeman.