Processing Speed Deficits Associated With Traumatic Brain Injury: Processing Inefficiency or Cautiousness?

Abstract

This study used speed-accuracy trade-off (SAT) methodology to test competing explanations for processing speed deficits due to traumatic brain injury (TBI): fixed limited capacity and volition. Twenty TBI participants and 20 comparison participants performed a visual scanning task with processing times controlled by the experimenter using a response deadline procedure. Results of the study demonstrated marked differences in SAT functions between the two groups. Participants who had TBIs were significantly slower on information accrual across processing deadlines (supporting a fixed limit explanation), but when early responding was allowed they chose to hold off responding despite being no more accurate in their responses with the additional time (a finding supporting a volitional explanation). Results of the study are discussed in terms of a resource allocation model that incorporates the influences of both processing capacity and volitional processes for individuals who suffer from brain injuries.

Keywords:

• processing speed
• speed-accuracy trade-off
• traumatic brain injury
• volition

Notes

¹The initial TBI sample size was 23, but three participants were eliminated from the analysis due to SAT performance data that could not be accurately modeled.

²The initial college comparison sample size was 23 selected from a larger pool based on approximate matching of verbal and reasoning ability scores to the TBI sample. Three participants were eliminated from the analysis due to SAT performance data that could not be accurately modeled.

∗Normative data with college students (n = 145) yielded a mean of 26.6 (4.8).

∗p < .01.

Note. Reliability estimates are shown on the diagonal and reflect Cronbach's alpha. Alpha estimates for model parameters were computed with the four independent parameter estimates obtained from fitting the model to each response window condition on each occasion, so they reflect measurement error due to both occasions and conditions.

³Figure 2 presents data from strict and flexible window conditions combined. However, analyses reported here indicated no group by condition interactions, so this figure can be taken as representative of the general form of the flexible window performance for each group.

⁴Another alternative explanation for longer response times by TBI participants in the flexible condition is that they did not understand that they could answer early. However, in an exit questionnaire given to all participants, they were specifically asked to describe each set of instructions. All study participants were able to accurately describe the difference between strict and flexible window conditions.