From Simple to Complex or Vice Versa: Sequence Effects on the Detection of Embedded Figures

In a series of studies concerning part - whole perception we have investigated effects of perceptual learning, and of systematically varied presentation orders on the detection of embedded figures. In the present study the effects of increasing and decreasing complexity orders on detection performance are reported. Stimuli were 170 pairs of whole and part figures. Half of them were positive items, ie the searched part was contained in the (simultaneously presented) whole. The other half were negative items, ie the searched part was not contained in the whole. The difficulty of all figure pairs was determined from earlier data. On the basis of these difficulty parameters three presentation orders were created: (1) increasing difficulty (from simple to complex), (2) decreasing difficulty (from complex to simple), and (3) randomised order. Sixty subjects performed each of these tasks in three sessions separated by one week. Effects of practice and samples were balanced by permutating the order of the three tasks. The reaction times and error rates for all presentations were registered. The results showed marked differences between the three tasks: The lowest mean reaction time was obtained in the presentation order with increasing difficulty. Error rate, on the other hand, was lowest in the decreasing-difficulty presentation order. For the random-order presentation error rate and reaction time was in between the other orders. Furthermore, differences in benefit from practice were observed between the three orders of difficulty. Results are discussed with respect to the question of how efficient search strategies may be learned and whether one can learn to bend the rules of Gestalt organisation if required.