Hitting a moving target: Perception and action in the timing of rapid interceptions

Different interceptive tasks and modes of interception (hitting or capturing) do not necessarily involve similar control processes. Control based on preprogramming of movement parameters is possible for actions with brief movement times but is now widely rejected; continuous perceptuomotor control models are preferred for all types of interception. The rejection of preprogrammed control and acceptance of continuous control is evaluated for the timing of rapidly executed, manual hitting actions. It is shown that a preprogrammed control model is capable of providing a convincing account of observed behavior patterns that avoids many of the arguments that have been raised against it. Prominent continuous perceptual control models are analyzed within a common framework and are shown to be interpretable as feedback control strategies. Although these models can explain observations of on-line adjustments to movement, they offer only post hoc explanations for observed behavior patterns in hitting tasks and are not directly supported by data. It is proposed that rapid manual hitting tasks make up a class of interceptions for which a preprogrammed strategy is adopted-a strategy that minimizes the role of visual feedback. Such a strategy is effective when the task demands a high degree of temporal accuracy.

Intercepting a moving target: effects of temporal precision constraints and movement amplitude

The effects of temporal precision constraints and movement amplitude on performance of an interceptive aiming task were examined. Participants were required to strike a moving target object with a 'bat' by moving the bat along a straight path (constrained by a linear slide) perpendicular to the path of the target. Temporal precision constraints were defined in terms of the time period (or window) within which contact with the target was possible. Three time windows were used (approx. 35, 50 and 65 ms) and these were achieved either by manipulating the size of the bat (experiment 1a), the size of the target (experiment 1b) or the speed of the target (experiment 2). In all experiments, movement time (MT) increased in proportion to movement amplitude but was only affected by differences in the temporal precision constraint if this was achieved by variation in the target's speed. In this case the MT was approximately inversely proportional to target speed. Peak movement speed was affected by temporal accuracy constraints in all three experiments: participants reached higher speeds when the temporal precision required was greater. These results are discussed with reference to the speed-accuracy trade-off observed for temporally constrained aiming movements. It is suggested that the MT and speed of interceptive aiming movements may be understood as responses to the spatiotemporal constraints of the task.

Bill Hayden at the Aldermaston Peace March in 1965

Bill Hayden at the Aldermaston Peace March in 1965. The march covered the distance between Ipswich and Brisbane, Australia. Marchers walked in relays covering approximately two miles each. Most relay sections were sponsored by one or more individual organisations.

Aldermaston Peace March April 5 1964 Brisbane Australia

Three men and a woman during Aldermaston Peace March, April 5 1964 in Brisbane Australia. The march covered the distance between Ipswich and Brisbane, Australia. Marchers walked in relays covering approximately two miles each. Most relay sections were sponsored by one or more individual organisations. Convoy of Volkswagon Beetles and FB Holdens can be seen following them. Facades of Elphinstones store, Masonic Centre and St Andrews can be seen on the left with the People's Palace in the distance and the Central Railway Station on the right.

Women during Aldermaston Peace March, Brisbane Australia 1964

Marchers with placards and aprons during Aldermaston Peace March, April 5 1964, Brisbane Australia. The march covered the distance between Ipswich and Brisbane, Australia. Marchers walked in relays covering approximately two miles each. Most relay sections were sponsored by one or more individual organisations.

Inala Darra Peace Committee during Hiroshima Day 1964, Brisbane

Members of the Inala Darra Peace Committee during Hiroshima Day 1964, Brisbane.

Graceville and District Peace Committee members with banner during Hiroshima Day 1964, Brisbane

Graceville and District Peace Committee members with banner during Hiroshima Day 1964, Brisbane, Australia.

Aldermaston Peace March participants 1965, Brisbane, Australia

Aldermaston Peace March participants 1965, Brisbane. The march covered the distance between Ipswich and Brisbane, Australia. Marchers walked in relays covering approximately two miles each. Most relay sections were sponsored by one or more individual organisations.

Dockers utility in Labour Day procession 1965 Brisbane Australia

Holden utility carrying members of the Federated Ship Painters and Dockers Union during the Labour Day march in 1965, Brisbane, Australia. Anti conscription banners can be seen in the background, and the facade of the Pearl Assurance Building.

Union for Civil Liberties Demonstration 1967 Brisbane Australia

People listening to speakers during the Union for Civil Liberties Demonstration September 1967 in Brisbane. The demonstration was called by the Trades and Labour Council of Queensland to protest against police treatment of university students and staff in Roma Street, Brisbane during a protest march. The march, from the University of Queensland to the city, had been held a few days earlier.

Young Labor demands better deal for Aborigines - Labour Day 1965 Brisbane Australia

Young Labor Association float during the Labour Day procession in Brisbane, Australia 1965. Placards call for voting rights for Aborigines, more education facilities and award wages.

Boys with placard during the Labour Day procession in Brisbane, 1965

Boys with placard during the Labour Day procession in Brisbane, 1965.

Demonstrators in Brisbane with banners and flags during Moratorium in Brisbane 1970.

Demonstrators in Brisbane with banners and flags during Moratorium in Brisbane 1970. Cameraman can be seen filming the march.

Kids in tram during No War Toys Christmas outing

Woman and children inside a tram during No War Toys Christmas party in Brisbane, Australia.

Tram at South Brisbane station, Brisbane Australia

Three men inspecting tram at South Brisbane station, Brisbane Australia, during No War Toys outing. WILPF (Womens International League for Peace and Freedom) banner can be seen on the front of the tram. The Women's International League for Peace and Freedom was founded in 1915. It works towards disarmament, political solutions to international conflicts, equal participation of women in activities, economic justice and the elimination of racism and discrimination. To achieve these goals, the Women's International League for Peace and Freedom organises meetings, conferences and campaigns.